Please share if you remember more about some of this than i can, but, From what i remember, once upon a time, there were lots of kmarts, toys r us's, and kaybee toy stores.
It all basically happened at the same time.
Walmart.
With that said, walmart could afford to rollback the prices of their toys, selling them for less than their competitors, and making back the money in other items they carry in the store, like food and such.
KB's, ToysRus, and kmart couldn't compete with walmart.
It also did not help that ToysRus had bad management, as did kmart. If you recall hearing about kmart in the news when they filed for bankruptcy.. Since all that happened, I remember some seibertronians freaking out about how toysrus's were closing left and right, and KB's were following in suit. Toys R Us ended up being sold to.. some new people, and if i recally correctly, they released a statement or something of that nature stating that they were either going to continue with the business, or basically sell it off, liquidate its stock, and gain the money back by selling the land that the actual stores were sitting on, and perhaps building whatever the new ppl wanted on top of the old toy store grounds. Without competitors, walmart would be able to have a sort of toy monopoly and charge whatever it wanted for toys and you wouldn't have any alternatives, except maybe online. Maybe we are already beginning to see this with the G1 ultra magnus reissue. $90?

As i recall speaking with one KB toys manager, he was saying something along the lines of how walmart is fixing to put toys R us and KB out of business within the next decade.
I'm not exactly sure why, as others before me here have pointed out, Kmart, ToysRus, and KB's usually have higher prices. Then again, they don't have the luxury of making revenue back on other non-toy items like walmart does. ToysRus did just have a TF sale, and target is staying competitive with Walmart. And believe it or not, i'm not trying to sound all anti-walmart, i am only doing my best to recall what i can of this part of TF history.
At any rate, whenever i can, i try not to buy my tf's from walmart, and prefer to give my money to Toys R Us or anyone else really.