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.
This is me right now, I spent ~$2k on a bike 11 months ago instead of getting a second car for our household and had no idea if it would work out. At 1500 miles, almost all commuting, definitely worth the money. I back of napkin calculated that it pays for itself somewhere between 2k-3k miles with saved gas, wear and tear, etc. Also my wife wanted to buy a Tesla as a second car, and me leaving her the car during the workday has essentially saved us ~$45k in that respect. In better shape, eating better, sleeping better, and bike commuting has a lot to do with it.