Wal-Mart style of protein supplements?

I usually buy like Optimum Nutrition but a friend of mine tells me he saves money by buying his protein powder at WalMart for a lot cheaper. You think this would be just as effective if you use a lot? Or is it a lot worse?

If it is a good idea, why does no one do it?  

the difference is not in the protien u will still get whatever ur body can take, but u wont get the bcaas or the other top qualitry nutrients that they put in brand name protiens. up ur mass or pro 5 are great.