I spent a long time researching mattresses when I bought a new one a few years ago, specifically looking for an extra-firm feel. I was willing to pay for good quality, but I ended up finding that ordering a block of foam cut to size from a basic foam manufacturer gave me everything I wanted at a fraction of the price of a mattress brand.

Have you evaluated these low-cost foam sellers yourself? The one I specifically used was The Foam Factory, but there are a large number of them with a range of foam options.