I bit the bullet in 2017 and got a Stearns and Foster mattress set. I think it was less than $2k for the set, queen size, at City Mattress, and they had a “zero percent interest for a year” thing going on. It’s one of the best purchases I’ve ever made.
You’ll find them for much higher prices online, it was going to the store that got me the deal. Find a mattress store near you that carries that brand and you may find a deal, too. It’ll save your back and you’ll sleep so much better.