
Brooklyn Bedding
Signature Hybrid
Durable, comfortable, adjustable firmness; excellent value.

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I went with a Zinus Short Queen Mattress - 8 Inch Green Tea Cooling Gel Memory Foam Mattress off Amazon about 3 years ago (or more) and found it was far superior to a regular mattress. Never regretted it. If you go this route, see if you can find a cover for it first.
We had this same mattress. Very pleased!
Sinus brand through Walmart is pretty good, it’s what my husband and I use and we really like it. It was nowhere near $1500. We have the 8 inch memory foam queen size and we paid less than $300 for it and have used it for over 5 years. We got a full size for a guest bed we had awhile back and everyone loves it so it was a good move.
I got a cheap 8" zinus memory foam mattress ($200 )about 6 years ago for the guest room. People still love it. I also got a more expensive ($1200) sleepez latex hybrid mattress that is pretty awesome as well. It's quality materials. I recommend the latex hybrid or a get a cheap zinus or novella or lucid from Amazon. The more you spend or dwell on the decision, you'll find more faults with it.
We just got the Zinus 8", as recommended by many people in an RV group were in. And I bought a mattress pad. The factory one made it 3 nights and now it's in the trash. We don't keep the Murphy in sofa mode all that much and the bed is always down for storage and travel. I don't have any recs for one with a fold.
I have a 7 year old Zinus 12 inch and it's still great. I just got 8 inch, I think, for my kids beds. Theirs are super comfy as well but it's only been a couple of months so I'm unsure about longevity.

Brooklyn Bedding
Signature Hybrid
Durable, comfortable, adjustable firmness; excellent value.

Sleep EZ
Organic Latex Mattress
Highly customizable layers, durable; but extremely heavy.

Helix
Midnight Luxe
Pain relief, side sleeper support; but some find too soft.

Purple
The Purple Mattress
Unique grid feel, cool; but heavy, expensive, polarizing.

Brooklyn Bedding
Aurora Luxe Cooling
Excellent cooling, zoned support for heavier sleepers.

Ranked #1
Novaform - Platinum 16.5" Luxury Hybrid Mattress

Ranked #1
Brooklyn Bedding - Titan Plus Luxe

Ranked #1
Purple - The Purple Mattress

Ranked #1
Sleep EZ - Organic Latex Mattress

Ranked #1
Helix - Midnight Luxe

Ranked #1
Sleep EZ - Organic Latex Mattress