that's why people that sell 15-20 a year are part time. The guys that sell for $2k or less are either making a lot more frames than that or part time.

I think you probably over-estimated taxes, but you didn't mention insurance, which is $2k a year

Someone on the top of their game can build a lot more bikes than 20 a year. The issue is that time interacting with customers cuts into the time available. But if you turn off the phone for most of the day, one a week or more is possible. I'm pretty sure that I can build a frame in a day, and with a little more tooling it would be less than that.