Everything has an opportunity cost. In this case, he managed to both go to work and build a house. He gave up his hobbies and in return built a house for "free" (gaining a new short-term hobby). How much are you and I giving up by reading HN right now? It's very, very difficult to attach a dollar value to opportunity cost when you weren't going to be doing anything money-making with that time anyway.
Agreed, but then the headline should have been "Guy has a fun time spending 1,000 hours building a neat looking house."
What bothers me is the bait and switch. It's bad journalism, but I would bet that the people who find this economically or ecologically "good" would be disinclined to change the headline because something to the effect of "dude has fun hobby" doesn't have the same "social good" connotations as the current headline.
