UGH. I don’t know that it’s totally illegal, but it’s a generally shitty thing to do to an author (who doesn’t get any kind of profit from it) and the publisher (who paid to print the ARCs on the good faith they’d only be used for review copies, not for someone else to make a profit off of). Now when I’m signing and it’s clear a person hasn’t read the series or isn’t like, “my kid/grandkid/student/wife/husband/teen is into this series” (or they don’t specify it’s for a blog contest or something) and they ask for just a signature, I always want to put in “To Ebay buyer, Enjoy!”
They’re marketing materials. They’re not meant to be for resale or purchase, and, believe you me, the people buying them for 10x and 20x the price are only hurting themselves. Why, why, WHY would you ever pay that amount for a version of the story that hasn’t been copy-edited and could change? Because you’re impatient?? The wait is always worth it, imo.
I am always stunned to see people buying ARCs, especially when they go for double or triple or more the cover price of the book. I mean, I guess some people want them for collections and stuff, and the book-hoarder in me gets that, but seriously, lots of ARCs say “not for sale” on the cover. And the only person who sees the money spent on that eBay ARC is the person who’s selling it — not the publisher, and not the author. That’s someone who got a piece of promotional material for free and then decided to make some money off it, and often a bunch of others.