I know some people that freedive-spearfish for a living. One of them is the reigning world champion, Patricio Saez, from Chile. He won the championship last year in Portugal. But he is far from being rich, and doesn't even own a boat. Others do much better, like some in Florida and the Gulf Coast who have big boats and use very expensive Scuba equipment. Of course they are subject to all legal regulations as commercial fishermen. And they dont waste fish as the trawlers and long liners do.
Now, the immense majority of the spearos I know eat the fish they capture, but to take food to the table is not the number one motivation for practicing this sport. If it were, we would rather go the nearest fish market and buy lobster or whatever the most expensive is, and would still save a lot of money, not to mention time. The truth is we spearfish because we like, or rather we enjoy it tremendously, and we spend a lot of money in equipment and a lot of time in maintaining it and tuning it, etc., because we love to do it, and enjoy our time in the water as much, if not more, than eating the fish. And when we take a big fish, or a fish exceptional for any other reason, we feel good about it and we take pictures to show to whoever we like. Some people call it a "trophy", and maybe yes, you can compare it with a trophy if you put the picture on your wall or even take the fish to a taxidermist to be able to bragg about it forever. But if the fish meat is eaten anyway nobody can say that it was wasted, or that we killed it just to take a picture of it, imho.