As soon as a seller starts trying to bounce around to potential buyers saying others are offering more, I'm out. I'm not going to participate in a blind/secret auction.
It happens occasionally. Someone puts up a game lower than market value, and they get flooded and get wise to the idea people might be willing to pay more for it.
Sometimes the seller just goes with the first person who commits to it, sometimes it develops into a race (whoever can get there first gets the game), sometimes an auction. Welcome to craigslist. It's only been getting worse with sources for project games drying up.