I had a magnetron replaced on a microwave last year. Sure it cost the same as buying a whole new unit, but the whole rest of the unit didn't go into the landfill, and the labor charge stayed in my local economy.

I'm bumming about my mattresses, actually. One of them is pretty old and I've hated it for the last 15 years and I'm not sorry to have to replace it. The other, though - while it's 10 calendar years old it's only had about four years' worth of sleeping on it, and it is way too new to be so completely sacked out. I've been sleeping with a pillow under my butt, because otherwise the hole in my mattress was giving me back trouble. And I do flip it regularly. Grrrrrr.