This is the free market at work, folks! If the seller asks too much for an item, I won't buy it, and that's the choice we all have. If the seller's items aren't moving, he'll soon drop his prices. If you don't like the price, there are plenty of other sellers out there!
Equally, if the seller is the only one with a particular item, he can darn well charge what he pleases; simple law of supply & demand. At the end of the day, no one can
force you to pay a ridiculous price for anything.