I know a few keen amateur astronomers who make extra cash by producing astronomical equipment for other amateurs. Some of them are very skilled, and could probably start a fully-fledged business if they wanted to, but they prefer to keep it as a hobby.

I paid one guy $400 to build me an equatorial platform for my 12-inch Dob. The value it provides me is way higher than the financial cost, and he could probably charge more for his work, but I think his main motivation comes from the satisfaction of building things he's proud of and that others can enjoy. Certainly, when I occasionally donate my time and knowledge at public astronomy outreach events, I find it very rewarding, especially if I can inspire children's interest.

N.B. By far the biggest weakness of Dobsonian (or any alt-azimuth mounted) telescopes is the lack of tracking, and thus having continuously to nudge the tube to keep objects centred. An equatorial platform eliminates this weakness, and I strongly recommend one to anyone who's frustrated with their alt-az scope.