Walmart selling LiFePo4 batteries $539

I have bought stuff from Amazon, Ebay and Walmart.com. The only problem was with a coil for my genset that I bought on Amazon from a 3rd party. The coil was bad right out of the box, after several emails from the seller telling me I ruined the coil and would not return my money, I called Amazon and my money was returned, but not without a lot of frustration. For my needs a $539 Li battery is still not cost effective. Maybe in a couple of years it might.