The mattress is by no means the only way to get a complete and restful night of sleep, and past a certain materials threshold, you can't get longer or better quality sleep with any amount of upgrades to your mattress. The marginal cost is likely better spent by buying light bulbs that phase out blue light in your evenings, or by taking melatonin supplements, or with a therapy device for sleep apnea, or blackout curtains, or any number of other supposedly sleep-improving products. At a certain cost point, you might as well climb into a spa-grade float tank, or dangle from your back-piercings, or sleep in a bounce castle.

I think that there is probably a bigger difference in sleep quality between a $300 mattress and a $500 mattress than between the $500 mattress and a $3000 mattress. Once the specific concerns that typically interrupt sleep are addressed, the returns diminish fast. There is no way I am losing an hour of sleep every night just because my mattress isn't good enough.

That seems awfully likely to me, too. I paid around $650 for a full-sized Sealy pillowtop something-or-other, apparently aimed at the hotel market, from an online mattress store some years ago, and it's been fine -- at least as comfortable as the ($800 in the early 1990s) Stearns & Foster it replaced. It's possible the Sealy won't last as long as the S&F did -- at least back then, the latter had a reputation for top-notch build quality -- but I have a lot of trouble envisioning any mattress in that size class being worth over $1000, let alone $3000.

Not for everyone though, but I bet if I could get them sleeping similarly from a young age, it would be.

1.3billion Chinese sleep on essentially padded wood just fine, for example.

Sex is a big plus for a mattress, though. On a padded wood Chinese "bed" it's just fucking horrible for whoever's on top's knees/elbows/wrists/contact points.