As discussed previously, GPA excludes eBay's fees. The sales on 7/3 and 6/22 were on eBay and were probably subject to the 10% fees. That means the sellers pocketed $1,552.50 and $1,435.50. Given that, OP's transaction would have occurred via Facebook Marketplace (which does not charge any fees), the only fees the seller would have been subject to may be PayPal fees (let's assume 4%) which nets $1,536 to the seller. That hardly sounds like a lowball offer when compared to the eBay transactions. Besides, as mentioned in this thread, it's a starting point that the buyer works up from. But the seller wasn't even willing to entertain it and instead mocked the buyer. Given that someone posted the book for sale for $1,750 from an LCS with an online presence, I'd much rather take my money and buy from them than deal with some d'bag seller.