PyroLobster and MaxBorken , I love you both and am proud to share a cape with both of you but I think this conversation has gone too far in the "sell it and see" direction.
I'll try a different gambit and see if I can make any headway. Maybe I can’t, we’ll see. I've argued in my other posts for the role of various types of knowledge in (accurately) shaping people's expectations about prices. Here, I'm going to try to be clear about why those expectations might matter.
The argument for obliterating the PC forum is that PCs add nothing of value and are just noise. The market will always yield a price and that price is the reality of the situation, regardless of what price-checkers might say about it. Fair enough. Simple, straightforward, saves a lot of hassle.
But the other side of the same coin (and several people have mentioned it in passing) is that the seller has to find the price acceptable before an item is actually sold. It's not just the case that the highest bid automatically triggers a sale. Maybe it would be more fun for buyers (and maybe there would be less noise on this site) if that were the case. In reality, though, this isn’t how it works. Before a sale actually happens, the seller has to decide that the price they're being offered is acceptable.
This is important because people when people sell items, there is something at stake. People sell items in order to continue participating in the economy. They're usually selling so that they can turn around and buy something else (a different item, armor, HoM crap, whatever). Selling is (mostly) about accumulating buying power. There are exceptions to this, of course, and I'd be happy to discuss those another time but they might be a distraction now. I'd guess that, generally speaking, selling items for cash is mostly about accumulating buying power.
So, with that in mind, when people sell, they have an interest in somehow knowing (or trying to know) that the price they're receiving will allow them to have the buying power they need (or the increase in buying power they want). I think this is the minimal criterion for finding a price acceptable. Without the sense that selling this item will improve their ability to do the things they want in the economy, the motivation to sell (and comfort with selling) dwindles. Simply receiving a price from the market doesn’t provide this. It only puts the seller in the difficult position of having to decide whether the proposed price is acceptable.
How do people decide whether the proposed price is acceptable? I think it can happen in at least a couple of ways:
- If someone has a specific purchase in mind, then maybe they can judge the proposed price for their item in light of this concrete goal. Will selling for this price allow me to buy what I want?
- Regardless of whether has a specific purchase in mind, maybe they can judge the proposed price in light of where it would place them on the scale of buying power (as it is known through recent sales of a wide range of items). If I sell for this price, that would allow me access to this tier or level or kind of item. That's the financial neighborhood I would be living in. Is that where I want to be?
Again, I think this is really the minimal criterion. By answering "yes" to one of these questions, someone can sell a Req 8 unconditional axe for 10k because it allows them buy those two pieces of wood they've been wanting. The "buying power" criterion alone can't be the whole story. There is much more to it. Maybe the next set of questions is about whether the price is high enough relative to how other similar items are priced by the market. Sometimes people don't bother going beyond the buying power issue because they're so fixated on what they want to buy next. Buying power isn't the whole story, but it's probably the starting point. But even this minimal set of questions (focusing on buying power) rests on a tricky assumption – that market conditions at the time of sale will match up (at least approximately) with market conditions at the time of their next purchase. Everyone reading this thread knows that the economy in reality is dynamic and confusing. How do people make sense of a dynamic, confusing market – at least to an extent that allows them to act and not be paralyzed by fear that they are crippling themselves financially and relinquishing buying power instead of enhancing it?
They talk to each other. Why do people talk to each other about prices of things? They may talk to each other for information, but a lot of information about previous sales is available anyway (although not a complete database like we have for weapon damage ranges or other research into loot tables). Something else happens when people talk to each other. They manufacture consensus (or pockets of consensus, or pockets of consensus that fight with each other, I don't know). In any case, they manufacture a layer of “knowledge” that helps to stabilize the random fluctuations of the economy (at least within a community that produces the talk and believes in it) and reinforce the meaningful relationships that provide us a way of valuing items relative to each other and forecasting sale prices. The talking that people do with each other is what sets the scene for certain prices to seem “right” or “wrong” or “high” or “low”. People use this kind of trick to make sense and find their way through all kinds of unpredictable and chaotic situations, including everyday life. People generate all kinds of cultural communities that allow the people participating in those communities to manage the inevitable unpredictability that comes with the fact that we are always moving into the future and that's always new. We've talked ourselves into living our lives as if things like "Christmas" and "middle age" exist, but they don't...at least not outside of the communities of people who talk as if they do exist and believe in that talk.
Without this kind of talk – if we strictly relied on what the market spit out when an item goes up for sale – there is none of that. Every price is right simply because it’s the one that happened this time. In this vision of the world, there is no way for a person to make any judgement about whether a price is acceptable. Actually, there is no need for a person to make that decision (really, anybody who decides that the market's price isn't acceptable would just be wrong). And that contradicts one of the fundamental things that we think we know about how buying and selling actually happens. People don’t sell unless they find the price acceptable.
So, my argument here is that price checks are important -- but not because they are predictions of what the market will yield. The market will yield what the market yields. I don’t think PyroLobster is that far off when he wagers that PCs are frequently off by 50% or more. But I’m also not sure that this is their true function. I’m arguing that price checks have a place within our economic system because they’re just one kind of talk that people engage in in order to give an understandable shape and a certain amount of predictability to the economy. This layer of knowledge and pretense of predictability is what lays the groundwork for people to be able to make the judgements they need to make in order to decide whether a proposed price is satisfactory. How can a seller decide if a price is satisfactory if the prices of other items (including the one they might want to buy next) are simply unknown and unknowable until the moment they're sold? There is no way. That would be crazy-making. Do price checks accurately predict what the market will yield? Not always. But I think PCs (good, honest, knowledge-based ones) will continue to be valuable to people because they are at least some indication of whether, in light of how the economy has behaved in the recent past, this person can reasonably expect to get the kind of boost to their buying power that they’d like to get out of the proposed sale. PCs are psychological tools but they're also tools for social coordination of the market. PCs have a psychological purpose – to give people a sense of being able to wrangle the underlying unpredictability of the economy. But PCs also have a social purpose -- to maybe make things a little more predictable through the generation of consensus. Together, these two functions provide a way for people to get a sense whether the best offer is also an acceptable one.
Just telling someone that their item has value and then throwing them to the market doesn't help them make a decision about whether the resulting price is acceptable.
Allowing one (or very few players) to steer the direction of consensus creates discrepancies of power that can lead to the disintegration of communities that generate economies in the first place.
Just an idea. As my mother likes to say at the dinner table, “Take what you want and leave the rest.” Fire at will 
