Crystalline swords are like BMWs. It's a poor person's rich person's car....
As someone who lives around London, I 100% get this statement xD I do think they are a lot more collector worthy and less memey then you guys are making them out to be hahaha, but they certainly don't hold up to the rarity of Swamp Clubs or Unconditionals for sure, possibly some req7.
The main point is that as time goes by there are less and less for many reasons all ready stated here. Since none drop any more demand stays high but supply is ever limited and falling incredibly fast.
In my personal opinion, it's the most accessible "premium" weapon (good luck finding a dwarven or serpent) but also just happens to be the most badass and "legendary".