When GS does the bogo type of sales If you have multiples the online store doesn't discount correctly, it only picks up the lowest. That's fine for two items in a buy one get one or four items in a buy two get two but when you have 8 items in a buy two get two scenario it discounts the four lowest items. if four items are $10 and four are $5, instead of getting two of the $10 items free and two of $5 items free you get four of the $5 items free. This has to be on purpose. I saved $60 by splitting everything into four different orders on the psp sale. I think I purchased one of every arcade compilation, rpg, and tactics games available.
It's different in the stores. I'm all the time buying old stuff when they roll out the buy two get one frees and I've never seen the stores pull the same trick, it's only ever online. I've even tried putting items in my cart by price level highest to lowest and it still applies the discount to the lowest of items.