I paid 1200 in total for my bed, a 'double' pocket sprung mattress + frame. mattress was about 650.
I don't know why so many people are kicking up a fuss about the cost of a mattress being £2000. A lot of people on here seem happy to spend more than that on a bike, but i bet they don't spend 8 hours every day on it.
if you think about it, 2 grand for a mattress isn't a lot for the use and longevity you get out of it.
My advice, get the best quality (not necessarily the most expensive) you can afford…..and try before you buy.