I make a little audio gadget. Something like a guitar pedal. My first product, I rather arbitrarily priced it at 4x my cost of materials. Then I began keeping

I make a little audio gadget. Something like a guitar pedal. My first product, I rather arbitrarily priced it at 4x my cost of materials. Then I began keeping records. I use PayPal for everything. It comes with a Visa card. At the end of the year, I download the entire year's transactions as a CSV and work out my numbers in a spreadsheet. I keep procrastinating on doing it in Python. Money in, minus money out, is my profit. Next, I have a decent estimate of my hours. I've tried to price my goods, so I can pay myself somewhere between $50 and $100/hour. I try to make very sure that I'm not robbing my family by spending time on a "business" that's not actually a business.