A piece of memory foam mattress can costs as much as a small car. Some of those claimed to be made from some NASA quality memory foam. I have tried them and it does feel nice to lie on the memory foam mattresses.
However, I won't ever buy something that expensive. I prefer to stick to some mattress that is not too expensive, yet cosy. This way, I can get rid of them and buy another new mattress in a few years. If I spent over $8K for a memory foam mattress, I will probably need to bring it along as my coffin. :)