> it will cost you 1 BTC to produce, market, and sell a single widget, and that it is only worth your effort if you can sell each widget for 2 BTC, a handsome 1

> it will cost you 1 BTC to produce, market, and sell a single widget, and that it is only worth your effort if you can sell each widget for 2 BTC, a handsome 100% margin. That's a 50% profit margin, not 100%. profit margin = 1 - cost/revenue = 1 - 1/2 = 0.5