There should be a limit for an item being posted in auction. Sometimes I see things being sold for 100x the original price. It should be max 2x the original value.
Why? It's a free market. People should be able to sell for as much as they want. If a buyer is willing to pay 100x the original price, then they can do that. Many times, the item is worth more than the stated price, due to the difficulty in gaining that item, etc. Take the GNG music block for example. No one is going to let that go for a measly 5000--if it was only able to be sold for 10k, people wouldn't sell at all (it wouldn't be worth it) or they'd just start selling in person, auctioning their items through global.
Kross already made some excellent points. I'll just add this:
If I auction something at 100x the original price, and no one buys it, I either take it off the market or reduce my auction price. If you don't think something is worth what its being sold for, don't buy it. Either find it / make it yourself in-game, or wait for a better deal (one usually does eventually come along). If it's a particularly rare or difficult to make/find item, it arguably IS worth the inflated value.
The in-game value of anything is not at all affected by demand, which fluctuates, but by the baseline value of the item, which also indicates how much you will get for it if you sell it in-game to a vendor, or donate it to a shrine.
This adds for an extra level of complexity and strategy when it comes to game play, because an item that is worth 47c in-game (and donated) can get me thousands of currants in an auction because it's a hard to get and in demand commodity.
There is absolutely nothing in the game that you NEED in order to play that you can't get through the game or at a relatively fair price on the auctions. The auctions are useful because they offer nearly instantaneous gratification and convenience.
This leads me to believe that this is a veiled complaint about a certain key or a beta/alpha item.