I bought a piece of 1.5 inch stiff foam to try to fix a sag in a bed. It didn’t work but having that thick piece of solid foam around has been a life saver.
Need something flat to put a laptop on? Throw it on the foam. Going to be doing something that requires you to be on your knees for a while? Get the foam!
It went from stupid purchase to something I’d gladly replace if it broke.
Some cursory googling for this turned up a value by researcher Alex Crumbie, though I didn’t find any papers about it. According to them however 30% of the world uses toilet paper, the majority consumer being China. The remaining 70% of the world finds other solutions.