In the future, I would suggest bidding on an item you're satisfied with the starting bid rather than trying to buy it for a lower price via PM 
Good advice. I don’t think it was necessarily a problem for him to try to get a deal via PM though. He should have however bid when his offer was refused if he was interested in doing so. Instead he gambled that nobody would bid and he would be able to use that as negotiation leverage. The gamble didn’t pay off, and the opportunity to own the item was lost. You can’t cry over spilled milk as they say.
TL;DR
Nothing to see here.