This was a really interesting read! Back in the day a friend and I started a company and Kickstartered a RPi add-on. The kickstarter campaign failed, but we ended up building anyway after one of the silicon manufacturers spotted the project and provided some FoC devices which changed the economics.

We spent oodles of time on it, learned lots, build a fairly simple product but ended up selling it through some of the bigger RPi retailers. It was all an excellent learning experience, and ignoring our time we made about 50p out of the entire batch of a thousand. Factor in our time and it was a complete financial disaster, but we were young and carefree and had fun doing it!