[mdibella]

Because they hired shitty programmers?

Seriously, it sounds like when they ship an item, they check the current price and adjust if it is lower. They do NOT, however, check to see if it was lower at any other point since the order was placed.

Since most of these PRS900 backorders have been waiting a month or more, they were placed at the original (higher) price. Since they won't ship this week, the pricematch check won't be done. When the sale goes off on Sunday, the price goes back up and when they ship it will look like the price has not changed.

By reordering at the sale price, your order will have the lower price on it already.

Of course, it is equally possible that this sale will be extended, since they can't GET the item. It's unclear to me why you would put something on sale when you don't have any to sell, but there it is...