I'm actually not sure about that. I was under the impression they were supposed to be cheaper (no cobalt, easier to manufacture, etc..), but if as a regular person you try to buy some from a reputable American distributor of a respectable brand they're pretty expensive. I don't know if the price of, say, Calb cells from EVWest is anywhere close to what an auto manufacturer would pay for something equivalent, but they do seem awfully spendy on the retail market.
Supposedly Tesla is going to use LiFePO4 in all their cars sold in China. It has less energy density, so I wouldn't expect them to do that unless it was actually cheaper. Or if they were somehow forced into it (e.g. government mandate to use locally-made or cobalt-free batteries, or inadequate supply of their regular 18650-cell batteries).
(I recently bought about 450 pounds of LiFeP04 cells for an electric car conversion, and it's the most expensive part of the project. About $6,000 iirc. That was buying from a local guy who has a huge stash of them from a cancelled industrial power supply project, and they were cheaper than anything I could find online, with the possible exception of some shady-looking aliexpress vendors. Not having to deal with hazmat shipping was a big plus, too.)