I had to replace mine this winter. I was outside of the 160,000km EV powertrain warranty coverage and paid ~$4,000.
Double check that claim that you're not covered because you bought it used. Mines used, and was a taxi prior, yet Kia footed the bill when it came to replacing the battery pack under warranty. I'm from Canada so Kia America for example might have a different policy, but that would seem..strange.
Best of luck!