It seems that Priceline policy is what ever the airline policy is. If you cancell your flight you are subject to the cancellation terms of the airline unless you buy refundable tickets. This just happened to some friends when we tweaked our PV trip.
Anything you book through Priceline bidding or Hotwire offer is simply a prepaid ticket or reservation. It doesn't make any difference whether it's a hotel room, air ticket, or car rental. Once the deal is confirmed, PL or HW gives the vendor the money and you get the ticket or confirmation.
Accordingly, all changes are at the discretion and option of the vendor. Most vendors will simply follow whatever policies they have in place for handling requests for changes for prepaid services. So if you have an airplane ticket through PL or HW and you want to change your flights, you may be able to do so but you will pay a reticketing fee as well as any difference in fare between the fare you paid and the fare into which you are rebooked.
Note that when it comes to such matters as refunds, the money transfer was between PL/HW and the vendor, not you and the vendor. Thus, the only entity that could ever get a refund from the vendor is PL/HW, not you. If you think you are owed a refund, as far as the vendor is concerned that is between you and PL/HW.
