Since there has (once again) been a thread in the PC section, that got terribly out of hand, I'd like to attempt to give a proper definition as well as say one or two words about the economy and conclude on why these vivid arguments occur.
I do realize that probably there will be people, who have the urge to defend themselves because they feel offended, however I'd love those to hesitate and reason about what I say on a neutral rather than personal perspective.
A price check should represent the value of the item in question on the market.
Thus it should give an amount that the seller may ask for on the market and be likely to be successful with (means he finds a buyer) AND at same time an amount that a interested person could try to buy the item for and likely be successful (means he finds a seller). Later on why a PC is exactly that.
That is what the person asking for a PC wants. Neither would he like personal opinions like "this is crap" or "it should be worth less" - those won't help him - nor does he ask for them.
Of course there are items difficult to PC and items more easy to PC. Some core skin q9 15^50 item is on the easy side whilst a q10 dualreduction defender is on the difficult side. A nick item is on the easier side, a q7 fellblade in white is on the difficult side. Why is that so? There are plenty of q9 15^50 core skins around and they are regularly sold. Nick items as well are a rather regularly sold item even though it changes weekly. A q10 defender or a q7 white fellblade on the other hand are difficult since there's barely any of those around, not to say they are unique. There can't be a market value for those - there is no comparison. STILL there are collectors looking for either - some desperately - and those have prices in their mind, which they find appropriate, they might however pay more, since they really want it, which might express itself via a upper limit they set to themselves or their maximum is limited by their wealth. A PC now asks: what price do I get / have to pay for this item? This is where the trickey part begins...
you could tell the amount that you find reasonable, the amount you'd pay for it - be it mental or wealthwise a limit (if higher than what you find reasonable) and both would kind of be valid as a PC on the first glance.
BUT that is wrong. That is your personal opinion. The buyer wants to know how much he'll have to pay in order to win against rivals, the seller wants to know how much he can get out of the item from those interested in it. That is what is the value on the markeg in either case.
Now to give the best possible guess on that you'd have to combine all the "how much would I pay for this item" of ALL the players around and see where that leads:
1. If the item is offered for sale the one willing and able to pay the highest amount will get the item on an open market, if the seller thinks the offered amount to be "appropriate or higher". If not the item will not be sold until sellers opinion or interests limit (be it of mental or wallet nature) change. - That's what is commonly referred to as "put it for sale and see where it goes" - a legit option to determine a price and potentially the most honest and best guess YOU can give - still doesn't give a price check and thus is a little out of place - a general big reminder in the header of the PC section should inform, that without a PC by several people in similar price regions a sale via private pm is a little like lottery - could go very well or very bad. Later on that. But putting it for auction is an alternative to a PC - it is not a PC.
2. If the person asking for a PC is interested in buying the item there may or may not be such item on the market. That is not the question asked by "give a PC" however. That problem is commonly referred to as "priceless" "there is no such thing" etc. Again that is rather a limited reply and won't actually answer the question asked. Either there is such thing for sale, in which case we go a similar direction as under point 1. or there isn't - in which case no trade occurs and no real value could be extracted from that info: one would have to suggest such an item hitting the market and mentally follow the steps mentioned (hint: "auction", "who'd pay most").
So what would be the value of the item on the market now? Let's think of an open market, say an auction. How much would the item sell for? The person willing and able to pay the most could get it - as the only one amongst the buyers - but only if the seller is willing to sell at that price, which is his personal value of the item. The price that it would go for is slightly higher than the-higher-amount-of-what-second-highest-willing-to-pay-and-the-sellers-value-of-the-item is, if still lower than what the person willing and able to pay most would pay. If the sellers idea of the itemvalue is higher, the highest amount the item would be possibly be sold for on the market is still the amount, that the person willing and able to pay the most is willing and able to pay, which in that case is the value of the item on the market - neither the sellers idea of the value of the item, nor the other buyers' limits hit that criterium.
In that case the amount the person willing to pay the most is willing to pay is the value of the item.
Now if the item is sold the amount it is sold for still isn't the value of the item: if the sellers idea of the price was low he will have agreed to a price, that was lower than the person willing to pay the most would have paid. If a person is interested in buying an item he'll have to expect to have to pay (slightly more than) the amount the person willing to pay the most is willing to pay - and thus the amount adressed in his PC.
So we can conclude: no matter what - the only proper amount that would be a PC is the amount the person willing to pay the most is willing to pay. The only problem is to know everyones opinions and find (amongst all those) the highest. - that means that any answers on discussive PC threads would have to promote higher values than previous replies - anything else would mean that either the person PCing first has already faultly given a guess without any proper knowledge or that the second person replying would not have got the idea of price check.
So in the end two things to summarize:
1. Post amounts you KNOW someone is willing to pay,
2. only if that amount is higher than those mentioned in previous replies.
Now few things to mention:
A sale via pm might be of advantage or disadvantage for the seller and the buyer: the buyer offering an amount might personally think of the items value as too high and offer too much, whilst in an auction he'd realize his mistake and correct it - advantageous for seller, disadvantageous for buyer. Or the seller might think of the items value as too low and accept a too low offer - disadvantageous for seller, advantageous for buyer.
Now what? A good trader knows his pricing and doesn't let trade partners know, thus he can on both options profit from the deals - commonly referred to as lowballing or scamming if done too extreme in ones personal value set.
This is where the PC comes in: to educate buyers and sellers about the items' potential.
In either case the specified applies:
PC = asking value of item on market = amount the person willing to pay the most for it is willing to pay
Which you choose is up to you - asking for PC or heading in on your own, trying to get a good deal.
So far about PC.
Of course people change, their wallet changes, their priorities change... even the supply changes and consequently the value of items changes.
This is getting excessive...
About the economy a few words:
Most people that have started collections at some point and stuck to it want to improve them, make them more special. That leads to the rare items getting more and more wanted - or if too common - neglected. That leads to one conclusion: stuff that still drops gets only interesting on the very rare end - as we see with q8 insc stuff, esp swords and shields e.g.. The common q9 15^50 core skin serves for heros at best. The next fact is: wealth in guild wars is constantly increased by farming and sadly botting. That leads to constant inflation - with botting even more rapidly. Hacking incidents of inactive accounts bring even more ingame wealth to the playerbase further increasing their wealth. With increased wealth the personal limits change in the same direction: for your dream item you are willing to pay more and more - possibly ridiculous amounts - and with the wealth that is even in the achievable range. That leads to a price increase in all items. But what does the seller want with money? Up his collection - often. That means the request of rarer items densens up. Also the buyer of the item might reach for higher goals now that his previous has been reached. That leads to immense price gain of rare items compared to common items. Usability is rather on a second point: to impress you need something extremely rare, not necessarily something useful. Sure there are collectors who do not want to impress others - but at least themselves - people strive for the higher. Sure there are people who just buy or collect usable items, but there as well many strive for the rarer. But the terribly rare items compared to rare items get again more wanted and thus even more rapidly gain in value. That is how q7 clean white fellblade got valueable - as well as q10 dualred. Defender. Sure those prices are ridiculously high - at least ridiculous to those not interested in the items or frustrated by their rapid price increase.
In the end if you afford a high value item it most likely increases overproportionally.
What happens on a global scale: the rich get richer, if they invest in items, the poor stay poor in comparison even though everyone gains money - welcome to free market economy 
in guild wars combined with high inflation lately due to said reasons.
So yes it still doesn't matter for the items value how much you would pay - what matters is what someone else would pay - and you'll have to do the same or not get the item (or be a good trader or scammer - whatever you call it - the line is thin - and fetch it without anyone else noticing)
So I'd conclude why the arguments in PC section: the amount someone on the market is willing to pay increases more rapidly than the respective personal value of some individuals - which leads to their contribution since they feel it's ridiculous and want to express that. - as long as someone is willing to pay more it doesn't matter what you think (and please - I am not adressing anyone in particular, just the reader - if you did read it this far :P) something that was garbage years ago today is the hot shit, since there is no supply of the nerfed stuff but an increasing playerbase seeking the uncommon - nerfed stuff comes to mind and woosh a purple staff that was merchfodder 10 years ago is worth thousands of ectos - an amount that was back when the staff was merchfodder would have made him the most wealthy player around. The actual problem was the nerf itself - creating such niche markets that could only densen up over years with no counterweight by new supply from farming...
Feel free to discuss with arguments of solid base - I tried to outline and argue everything reasonably and conclude logically.
Thanks for the attention - lets get the PC section a little calmer on the rare items.
And without wanting to promote myself in any way I'd think such a clear philosophy would be appropriate in the PC section.
