My old bed cost, I think, about $1,500 and was too big — Caper and I rattled around in it. It was also over 10 years old. I got a Wirecutter recommendation for a compressed foam mattress that you can order online and it comes in a relatively tiny box — for less than $300. Uncrate it, and over a day or two it expands to a full 12″ deep mattress. I bought one for Matthew, and he liked it, so I decided to upgrade (and downsize) my own bed.
Caper has already claimed it.