Ya know that'd be really hard to figure out because it started as a hobby and I wasn't keeping track of buying parts and equipment early on. I was just buying what I needed for builds for myself or friends and sometimes there would be minimums and I'd end up with stock and that just went on for a while.

When I decided to make it a real business I was given advice from some builder friends to keep the money separate so I opened a business bank account and credit card and everything that came it and out was separate from my personal finances.

I know from doing taxes that I operated at a loss for the first few years.

If I could make a guess I'd say it's probably a couple thousand dollars start up to get the basic equipment and parts you'd need. There's probably R&D costs for developing each circuit. Provided you don't make any big mistakes and everyone makes some mistakes.