On the flip side, using your $125 floor example - if the guy gets auto-rejected at $120 and doesn’t subsequently place a higher offer, would having the opportunity to try and negotiate even be worth it? Would he even respond to, say, a $165 counter? With the floor price in place, less potential hassles in my view (unless of course you get my favorite message - “hey bro, what’s the least you’d take for this book?” And...block).
Certainly an argument to be made on both sides, ultimately it comes down to time vs. opportunity.