Due to the cryptocurrency mining craze, parts, especially GPU's, are expensive as fuck right now. Most cards these days are selling well over MSRP value. Pre built is actually a good option right now. I grabbed a pre built PC off an Amazon sale with a GTX 1060 in it for $650, which is pretty cheap these days. Best bet, IMO, is Amazon or New Egg. If you want to build yourself and get parts, I would look the prices up on Amazon or PC Parts Picker and then go to a store that does price matching. You'd be paying out the ass at a place like Best Buy. At least Fry's does price matching, not sure about Best Buy. Another place you could try is Costco. I would avoid Wal Mart as their pre built PCs are complete garbage in my experience.