This is one of those crazy cases where parts of American population were seemingly hypnotised by advertising and are spending insane amounts of money on a commodity item. Here in Poland, the most I've paid for a mattress was an equivalent of $130. I've never had problems with them.
We ended up buy a model that was about $2000 just because we could tell the difference between the $700 model. But yeah, why is it $2000? What value is there actually in the mattress that justifies it? And if a cheaper option exists that would allow one to exist within one's needs, why not get that instead?