How did you chose your new mattress? I've had a hard time knowing from the short impressions in a mattress store if that mattress is really what I want or just feels nice for 5 minutes in a store
Cheap spring mattresses seem to be getting harder to find online. I believe the margins are much higher on memory foam products.
My wife got a foam topper and an 'under mattress inflatable thing' for my bed about 10 years ago - it was like sleeping on a new bed. I think it was around $150 at the time. Possibly getting a new bed this year, but those gave new life for a long time.
A bit of a hassle, but well worth it though.
But it's a bit of a compromise. My girlfriend hates foam mattresses even though I thought they felt great. This set-up lets me get a somewhat similar feel of sinking into the bed while being well supported.
She's also much lighter than I am and wants a soft mattress, so her side of the bed is softer.