In all fairness..We only know that NAV pm his offer because TS chose to say it here.
The rule of not bidding via pm is simply to allow open/fair bidding .
I see no need to give TS stick for accepting $150 offer. Anyways if NAV really wanted to buy at 150, he could just have joined the bidding at $150. I don't know why he did not. Maybe he was asking for fun.
As for TS , he was simply trying to clear ASAP. He could simply have inserted the "buy now price=$150" clause at any point without repercussion.
Though I will be wary of anyone with an incredible offer but choosing not to bid.