No need to call it a Scam. it is almost certainly not how it was intended to be used, it is exploitable, however, and in the crypto space, something that is exploitable gets exploited. in this case, probably by bots.
bidpay was confusing, but it was optional. my first few bids on a bidpay auction were terribly done, because i didn't understand it. i'm guessing most auctions with bidpay were done by people who didn't realize that it discourages bidding.
but the fact that it discourages bidding, meant that while i didn't get to bid on some cards that i might have otherwise been bidding on, other times, i got cards cheaper than i would have, and in a few instances, i made money from bidpay and won the card.
sadly, that is because bidpay isn't a good system, and i can't think of a simple fix for it.
but that doesn't mean its a scam, in fact, that is highly unlikely. it means that it isn't a good idea for sellers. they are literally paying extra to discourage people from bidding.