I purchased a 3″ latex mattress from ebay. Ebay sounded pretty sketchy to me at first, but it was a great choice in the end. I didn’t want to deal with a mattress salesman, and didn’t want to overpay for something I would most likely be disappointed in. Trying out a mattress at a store is useless. A mattress is a personal purchase, it is different for everybody. For $270, and several good reviews (aside from ebay reviews), I thought it was worth the risk. It was one of the best purchases I made. Latex is not supposed to wear out like memory foam, and can last a very long time. Another benefit is that you can fold it up and get it into a small car (I’ve moved 3 times with it). The ebay user is mattress247. My ebay id is arsk3121… i’m not affiliated with the seller, other than the purchase I made that was awesome.
Some downsides… it is a little more awkward to handle than a regular mattress because it is much less stiff (you can’t stand it up on it’s side). I assume most people would buy a much thicker mattress, and the price will naturally go up, but i’ve been happy with the depth of mine.