I prepared an excel sheet in which I compare the prices with Amazon.
Yes, their normal prices are higher than Amazon almost all the time, so bear in mind that the discount is not shown on the site but only applied at check out! With a few exception most stuff is cheaper than Amazon after applying the discount. I have a suspicion though, that they did 25% discount this time to be able to achieve that, as some stuff is cheaper buy just THAT much.
Another reason I prepared the excel list on Monday was, that this way I can now make sure they don't raise prices during the sale to minimize the impact on their side. I will order on Monday, I think, will report back if I find oddities.
I just checked my list and only one out of the almost 30 titles has a higher price now than a week earlier (Terminator 2 Blu-ray, regular). Over the list of titles before the sale it averaged to 7% higher at DD and now during the sale DD is in average cheaper by 20%.