Just used prime to order a
memory foam mattress with really good reviews.
Went to a few local stores where the sales people are all preconditioning you for what you will feel when you lay down. How about I lay down on the mattresses from $5999 to $1999 and when I get up I'll tell you how and what I felt. Honestly all of them did fine and the degree of separation didn't track with price.
So $429 for a mattress from Amazon with a something like a 45 day standard return policy (Amazon has a large item return department for items like this).
It will be interesting to compare this to a $2700 Tempur-pedic.