Some people say you can't include your time in the calculations. IMO,if you don't. that would be akin to someone bringing you a bike, a pile of parts and expecting you to restore it for them free. I (mostly ) enjoy working on them and derive satisfaction from a well finished job, but I'm not going to do it for free for a stranger who probably has more money than I. Any " profit" I make just gets channeled into the next project, so hobby is self funding.