That stamp was listed on
ebay at a Buy It Now price of $250 by someone in "Cave Junction, Oregon" with no other sales of anything. It did not sell. Needless to say, this seller is hardly likely to be a stamp dealer of any kind. More likely, it's some clown who "heard" that red line stamps are more valuable and so decided to try to sell one he had found which he believed was "rare". It's not rare. The whole thing is completely silly and does not even begin to fall into the category of "stamp dealers" trying to cheat anyone. It falls into the category of thousands of other products listed on
ebay as "rare" simply because the sellers thinks they're rare. If you own one of something, it may be rare to you, but if it's an old sock, believe me, no one is going to want it. I'd ban use of the word "rare" from
ebay entirely.
But to denounce
ebay because some sad sack seller listed a ridiculous stamp at a price that's too high seems a bit much. It's a free marketplace in which anyone, no matter how foolish they are, can try to sell things.
ebay is more like a flea market than a store, and flea markets are filled with ridiculous junk. It doesn't form some kind of stamp dealer conspiracy. Red line stamps are a phony product and any halfway informed collector knows that.
If you have some basic knowledge of the stamps you are buying, and that would include use of a catalogue, and if you buy from a reputable dealer (a member of the APS and other organizations who has been around a long time, etc, etc),
ebay is as good a place to buy stamps as any other. But you need some knowledge and need to be careful.
You might as well denounce "stamp shops" because of a few dealers overcharge for stamps. The problem may be related to
ebay not policing its stamp sales, but it doesn't see that as its job -- for good or ill. It's a neutral marketplace, and it has no interest in hiring a panel of stamp experts to constantly monitor sales for authenticity. That would involve thousands of sales of stamps, an immense number that could not possibly be policed carefully.
I do think
ebay should (and perhaps they do) remove dealers who repeatedly sell bad products. That's just common sense. They might employ one (1) stamp expert at least part time to offer opinions of the legitimacy of stamp products, especially the ones questioned by purchasers. This would help point out the bad guys. Beyond that, though, they're not going to hire a dozen stamp experts to scour the listings. There's no way they will do anything like that. If they did, they'd also have to do the same for coins, baseball cards, autographs, automobiles, artwork, jewelry and watches, and on and on ad infinitum.
I also fault
ebay's rating system which is absurd. It's either 5 stars or you're in trouble. Ratings means a gradation of evaluations. If ratings were more legitimate, dealers might be more careful. I suspect a lot of buyers don't even bother to rate their purchases because you feel you have to give a five or nothing.
Collectors need to know what they're doing, too. Dealers who will not accept returns should be avoided. If you spend a great deal of money with a dealer, you need to get your stamps authenticated immediately after you purchase them. Even better, do your homework before you buy, and buy only from the most reputable, long-established dealers. And return anything that isn't up to the most convincing standards. And, last, post your doubts about dealers here or elsewhere if they're based on legitimate concerns.