You also have to account for the fact that other people might think you're lazy or self centered because you don't want to spare some time to at least try to help them. Not saying that you're a bad person for refusing to provide free tech support, but your math is not entirely flawless.
Unless having a reputation for being lazy and selfless leads to more tech support calls, I think the math still works out on this being the least amount of work to get rid of tech support calls.
Whether this is a good idea or not is a separate question. Personally, I help my friends and family when I can.
