[airbreather]

I have a friend who wrote a technical book in a non computing field (sort of agriculture for home/small group use).

He couldn't get a publisher interested, so he self published, took well over $100k first year.

He had a subject specific forum he ran and for some time was #1 google hit for his specialty.

He also had converted his back yard in a bunch of experimental demonstration systems, so was pretty well living what he was selling.

Point is he probably sold less books, for much greater profit, but he already had an audience.