The first thing that you got to remember is that the objective of businesses like best buy and so on is to make profit. And it is impossible to make profit if they keep having great prices, the same goes for other retailers out there as well.
Basically what I see is a pattern in which when one store has a sale or something like that the other one has a bigger price for the same product and vice versa right after that.
So all stores offer a good price and it's not just best buy, but the timing of when you buy it might make it great. For example something might be lower today, but even more lower somewhere else after a while later.
The store doesn't matter that much, prices and all that keep changing all the time, so if you really want to get something just look around and see where you can get the best deals and get it, there's nothing that proves that only one place has to have the best deal.