The first few plumbing jobs I did myself were a net loss from time, tools, materials. But I've made it up since then. Also, I think it's not always direct - tinkering with the car has made me more confident in plumbing and vice versa. A few years of that and I was happy to install my own dishwasher.

So for me, I'll always spend time on this sort of stuff if it's within my reach to do a decent job.

As far as disposal goes... yeah, most stuff I sell on Marketplace or Gumtree would be a net loss after wasting time dealing with people (and scammers, who belong in their own category). But I hate to have things I used and enjoyed just die alone in landfill.