If people were perfectly rational robots, this could work. Also, sales jobs wouldn't exist and politicians would be held accountable for their promises.

In real world, sales tactics work. People can be influenced to pay more than they thought they're willing to pay. Scalpers know this and exploit this at scale. A Vickery auction gives basically zero opportunity to get talked up. People will bid at the "thought they're willing" price, and scalpers will outbid them. Then the same people who underbid on auction will go to eBay, see it listed at "influenced to pay more" price, and buy it for much more than they bid.

And yes; the vast majority of eBay auction bidders are indeed scalpers, whose day job is to look for cheap deals that they can resell for more. It's extremely rare in this day and age to actually take advantage of eBay bidding to buy in-demand stuff on the cheap. It's much easier when there's "buy now" option but you need to be fast and lucky because you're competing against scalpers here too. Of course things are different for stuff that few people want in the first place - scalpers are not interested in those because they're too hard to offload, so you get your fair chance.