There's only one person buying those cards right now. You
Right. And this is the fundamental reason why all the "OMG! PEOPLE ARE SELLING TOO CHEAP AND RUINING TEH MARKET FOR EVERYONE!!111!!!! STUPID COMMUNITY" posts make me chuckle a bit.
There's a huge disparity between the perceived vale of, for argument's sake, a foil card between the seller and the purchaser.
Purchaser will simply not buy if it's too expensive. But seller's seem to think that if *all* cards have parity, then the seller will increase his expectations and what he is willing to pay.
This simply does not happen in practice.
So ultimately, you hit a stalemate with an asking price that the seller is unwilling to reduce and the buyer is unwilling to pay. When you hit this point, the following happens:
1 - Someone throws the same item on but cheaper
2 - Seller panics and tries to buy up the cheaper item to artificially inflate the price
This can become a vicious circle, and you end up with sellers who own four or five of one item, without the capability to sell these cards on without making a loss. A very precarious position to be in.
Regardless, the main reason that this is a highly dangerous game to play is that the market is, by design, deflationary. Prices will always go
down in the long term, because there is an infinite supply of new trading cards flooding onto the market, but a finite amount of users willing to purchase. As more and more users craft their badges, the need to buy these cards reduces further, causing more cards to be placed on the market. At the same time, more of these cards are dropping and being listed on the marketplace. Net result - prices regularly drop to more accurately reflect the buyer's perceived value.
Artificial price inflation is a game you cannot win. Someone will always be able to undercut you somewhere along the line and leave you holding a lot of real money's worth of fake trading cards.
In fact, IMHO the "problem" with the marketplace is not the sellers setting prices too low, but instead the sellers setting prices too high and expecting to make a quick profit from their fellow community members with minimal effort.
TLDR; Always remember that the market is driven by supply and buyer demand. The longer prices remain high or are artificially inflated the greater the probability of a huge correction.