Yeah, that's kinda my theory: I only buy when a sale is going on. And I made it a bit of a sport's competition to find the best price during that, combining best offer from different shops, coins, shop and AE discount codes. Sometimes they add up to insane discounts where I thought that cannot be intended. A few do take several hours to actually be confirmed which makes me think there was a manual check going on in the background. But so far they all got confirmed in the end. I guess for most things a sell is a sell.
I think it is very unlikely that I will ever find a product in my order list where the current listing price (w/o discounts codes) will be lower than what I paid for it.