The good, the bad and the WTF of Wallmart!

I rarely go to Walmart, and it's usually only when I need to do an oil change and don't have any left at home. Been buying it from Costco more often, always cheap there.
Unfortunately we do the biggest part of our shopping there as there is only one other store in town and it's more expensive. I keep reading people saying that they don't go there, if that's the case then how can they be worth billions so somebody is shopping there