Poor Edge Support, Wife Choose, I'd Go Cheaper

I'll acknowledge that all foam mattresses are NOT the same and that I've gotten a better nights sleep consistently from this mattress than my previous mattress which was 7 years old, thinner, and cheaper. But of course it does. The edge support is rather a joke (the top, especially, collapses when sitting in bed watching TV and my pillows slip behind the top of the mattress). Some of this is endemic to foam, but it could be addressed with some form of edge reinforcement/firmer foam. Basically, it's a $1200 queen size stack of foam. It's better than the 7 year old $300 queen size stack of foam I had before in initial quality and in fit+finish. But it better be. If I had more than one bed at home, I'd try one of the 12" thick foam mattresses on amazon which are $350. I love the thickness of this mattress, but I'm rather damn sure you could get that for less than the $1200 (and that was with a discount). Supposedly has a long warranty, but I'm at a loss for what that means in reality. They say indentation greater than an inch. Relative to what? I suppose I could probably get a replacement mattress every couple years out of them (we're 18 months in) but that seems silly, wasteful, and tiresome. We choose this bed because the wife has back problems and this is the one she wanted (based on online reviews, it was also the most expensive). Call me a skeptic, but I'm pretty sure we could have gotten 90% of the bed for 30% of the money elsewhere. But, happy wife happy life.