Isn't it always a risk you run with ANY performance but particularly first preview?
They can't sell you tickets that they don't have. Perhaps full price tix holders rec'd notification a little earlier. It SOUNDS as if they tried to pick a date that had the MOST availibility. (BUT: I would have thought, to be honest, that they would have said you could re book your tix ANY time during the previews...but not guaranteeing where your seat could be.)
But I don't think they are out to get you or to create any kind of $5 ruse.
If we're not having fun, then why are we doing it?
These are DISCUSSION boards, not mutual admiration boards. Discussion only occurs when we are willing to hear what others are thinking, regardless of whether it is alignment to our own thoughts.