The conclusion of the podcast was "If you spend $800 you're probably safe, below that it's hard to know if it's good or awful. Above $1500 is too much."

Considering Marriott/Hilton/IHG requires their hotels to use a 10 year warrantied mattress that only costs $250-$300 each, I'd say even $800 is too high. Even though that's wholesale price, doubling should be enough to get a single unit price.

People would be better off investing in some HIIT cardio excercise if they're looking for a good night's sleep. And eating less / more nutritious food.

Exercising and eating right aren't 100% fungible with money. That's not even close to the blocking factor for most people.

The extra $300 is what you pay for going with a reputable brand, because unlike Marriott, you don't have the time to figure out which off-brand mattresses are crap and which aren't.

Book a room at the Marriott, go in, rip the sheets off the bed, check the manufacturer on the mattress tag, go buy your mattress from them.

(And enjoy the rest of your night in the hotel)

They're not off brand, they're Temper-Sealy or Simmons.

In that case, your assertion that "doubling should be sufficient to get single unit price" was wrong, cause you aren't going to get a queen from either of those companies for $500.

My current mattress is a $900 kingsize Casper.

It replaced a 10-year-old Tempurpedic that cost around $4K.

The Casper is a better mattress in EVERY WAY so far (had it since 2015).