Recreational lobster diving can actually be done in shallower water by snorkeling, which is how I do it most of the time. Even without all the scuba equipment, the sport can still be expensive. Normally you have to go somewhere away from your home/work in order to do it. You either need to have a boat or know an accomplice with one. Then you have to spend money on the boat's fuel and anything that breaks in it. If you are going for more than one day, then you need a place to stay (which will more than likely make you shell out some dough). The legal limit is 6 lobsters per person per day. That means that even if you find a nice spot with 200 lobsters in it, you can only take 6 of them until tomorrow. After you add up all the costs, it turns out that the lobster sold in stores is actually cheaper. Just leave the work to professionals and the market system to leave you with high quality lobster...and you don't even have to risk swimming with sharks to get it.
For some reason, I have the perception that most people think highly of lobster. It's a great meat, and a little expensive. Refined. Tasty. Desirable.
How is lobster diving like getting freaky? Most people value sex...some of them might value it a little too much (I think they omit some of the costs in their mental cost-benefit analysis). People spend a lot of money (AND OPPORTUNITY COST) in order to get other people to get them off. Men will take women out to nice restaurants, buy them shiny rocks, and all kinds of other stuff in an effort to persuade the women to give it up. Turns out that it's probably cheaper to hire a professional prostitute. This leads me to the conclusion that there MUST be some other benefit to having a girlfriend/wife/hook-up provide the desired service rather than a random (or maybe not so random) whore.
Conclusion: something about the hunt, the challenge, the possible elusiveness of lobster (or chocha) makes the ones you catch yourself taste even better. Overall, they're worth more. One reason might be because you hand-selected your own catch.