$148 total: https://www.ikea.com/au/en/p/agotnes-foam-mattress-firm-light-blue-50480865/
https://www.ikea.com/au/en/p/grimsbu-bed-frame-grey-60458760/

I’ve had that for 4 years but I’m also someone who happily sleeps on anything from air mattress to particle board and be reasonably fine the next day (I have the equivalent of that mattress. Mine has been discontinued.)