Well, the one I've found to be the most comfortable is this one. But best for me and cheap are relative to the individual. Sleeping on the ground isn't an option for me anymore, if I want to walk the next day.
That is a good cot. I've slept in one. Any of the army style cots are pretty good and sit higher. I would suggest a 36". I have a 28". It is good but needs some room.
We slept on the ground last year. Rough doesn't describe it. Took a few days for my back to get back to "normal". I don't mind paying a little more of its worth it