You must be talking about the used stuff. There are a lot of sellers listing new stuff and their prices are higher than regular online retail, a LOT higher in some cases.
But what baffles me is why someone would bid up to $405 dollars (not including shipping) on a mic that he coulda bought new and had shipped to his front door for $320? (I may have already voiced that question in another thread....sorry)
But many times what you say is quite true. In the not too distant past I have won mint condition mics for $99, $140 and $280 that retail new for $200, $289 and $350. I dont think I've ever lost money buying and selling guitar speakers on ebay. Got a steal from Avatar once, four Hot 100's for $100 bucks shipped! The guy at Avatar told me it was a fluke that happened because the auction ended on a major national holiday when nobody was watching or paying attention...... except me.
Another thing I wish people would learn is dont bid until the end. Dont bid on something just to be the high bidder. It's so frustrating to see a nice $350 dollar mic sitting there at $63 bucks for 5 days, then some rookie comes along and bids $65.50 while there is still 2 days left. An hour later the price shoots up to $229 because the first guy is more interested in being king of the hill. It's a mistake to treat ebay like a real live auction where you try to nickel and dime the bids one after another. All you are doing is driving up the price. If everybody would mentally decide their max bid and then wait until there is 15 seconds left on the auction, things on ebay would sell a lot cheaper!! Unlike a live real auction, with a timed auction the point is not to be the high bidder, the point is to be the last bidder.
Usually you can get a better deal if you are patient and wait, set your max price you will pay and stick to it. Just 2 days ago I resisted the temptation to bid over my max on a mic I was itching to hold. Sure enough I found one in better condition a few hours later and won it for less than my max dollar.