I have a king-size solid latex mattress. I’ve had it several years now and still love it. I think it cost me around a grand, which was way more than I’d ever thought about paying for a mattress, but I had to do something so I could get out of bed in the morning without needing help. My back immediately improved.
It came with a 20 year warranty, from a long-existing local business that makes their own mattresses. They had different firmnesses you could test, and then they made a mattress to your order. Mine is extra-extra-firm, with a very soft layer on top. It sits on a platform, no boxsprings. We try to remember to rotate it, but it doesn’t get flipped due to the top layer. (If we hadn’t done that, it could be flipped also.)
It’s similar to the Tempur-Pedic-type foam, but it’s not heat-activated and not quite as “solid” feeling. (My first thought when I tried a Tempur-Pedic mattress was “it’s a soft rock!”.)
I didn’t go with the T-type foam because several salesmen mentioned that it tended to be a very warm mattress. The foam is heat-activated and tends to hold/reflect your body heat. Since I’m a heat pump, that seemed like a bad idea.
My ectothermic partner bought a knock-off Tempur-Pedic-type foam mattress a few months later, and loves it. They were a bit cheaper than the latex (maybe $800?), and again came with a 20 year warranty, this time from the manufacturer. It came with a platform that looks like a box spring, so it could go onto a regular bedframe.
My other partner hates the T-foam, I think it’s fine. It does have a tendency to hold you in place once you’ve sunk into it. Since he’s a restless sleeper, it wakes him up all night when he tries to roll over and can’t get out of the hole he’s sunk into. He absolutely loves the latex.
I prefer mine, and would buy it again, but if I couldn’t get that I’d probably go with the T-type foam.
OTOH, we’ve had a number of friends test both mattresses. I think most of them like the T-type better. I know the one couple that have actually purchased a mattress went that route. It’s been a couple years and they still like it AFAIK.
We didn’t find any regular mattresses that we liked, and we looked at everything available. At the time, I think Tempur-Pedics were running around $1600, and regular mattress/box springs sets were anywhere from $600 up to the roof. I’ve always hated pillowtops (I like firm), and the Sleep Number things sucked big green eggs.