There has been a big revolution in mat design and construction over the past two decades. About the closest thing to that in the surfboard world was the blowing up of Clark Foam which unleashed a lot of innovation in the construction world.
Yep. Amazon. Read the reviews and you can score a great mattress for less then $500. I bought a queen last year for a guest room for around $300 (inner spring, plush top), and I like it better than my $1,200 mattress in my bedroom. https://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias=aps&field-keywords=mattresses
Memory foam mattresses on Overstock.com. I spent about $400 on my King size and it's the most comfortable mattress I've ever slept on.
I will need to test with hot Hindu women whilst riding said mattress down the face of a Belmar 23footer and shotting piers. Please and thanks
Get an air mattress cheap and comfy but if you bring home a big gal you may pop a leak just have gorilla tape on ya to plug the leak!
Based loosely upon the medical advise in this thread, I purchased a Purple mattress. It turned out to be awesome and "fixed" a sharp pain I was getting in my back. I love it so much I bought a Purple cushion for my office chair. Really cool technology. I recommend!