Thanks for the responses. I've had a little more time to calm down, and I'm no longer furious. But I am still pissed (how's that for a fine distinction?).
I do want to emphasize that about a third of the cards are of decent enough autographs, the usual suspects of players active from the Forties to the Seventies. What seems to have happened here is that these lots all came from a single collection, belonging to a fellow named Al Hein (anyone know of him)? I know this because there were a few GPC's mixed into the mass of 3x5's with his name and address on the front, and a Google search indicates that Hein died in 2020.
Apparently, Hein wrote to every person (or almost every person) playing professional baseball in the Eighties. Most, obviously, never made it to the big leagues. It's notable that the major league players I found among the unidentified index cards were mostly cup of coffee players, 1980's minor leaguers who made it up to the majors briefly in the early Nineties.
As for asking questions about the lots beforehand, it honestly never occurred to me that the signatures could be those of minor leaguers. Silly me.
I suppose I will take solace in the fact that the identified cards (the ones with the name typed on the front) include some pretty good signatures. But yes, when you bid on an auction of this size, you're looking for a bargain. I'll pay full retail for a signed Topps card or any one of a number of collectibles, but 3x5's are precisely the sort of collectible I would rather get at the bargain level.
And for those who are curious, the auction in question was the recent one conducted by Wheatland. I expected better of them.
Alan Kleinberger