My wife picked up a Double size thick piece of egg-crate foam from a futon supply store here in town. I must say, WOW is it comfy. I would say save some $$$ and just get the foam for camping. It rolls up to ohhhh like a 2 foot diameter circle as wide as it is, but it's so worth it.
The air mattress, well, I just don't dig them anymore. With as much as I use them for camping, there would always be a point where they started to go flat. In the middle of the night. Waking up to back pain. I'd rather sleep on the ground LOL!
I think my wife paid under $100 for the foam; seems expensive, but it's some quality stuff that's quite comfortable.
Clay