HypersomniacLive: If I'm not terribly mistaken, during this type of sales, the checkout page expires after the game has sold out.
Neverfree: Thought so to, but I purchased a few even after the sales were hours done. Just has the be in the checkout phase :)
I suspected the system might be engineered this way. Still wondering though if the counter goes down at this point, or only when a checkout completes. If the former, then games could be undersold by people cancelling from the checkout. If the latter, then games could be oversold by the system honouring checkouts in progress even once all allocated items are sold.
My suspicion is the latter case.