In most cases a couple of years worth of profits from monopoly should suffice. In reality it depends on how much was spent on the initial innovation. One trick

In most cases a couple of years worth of profits from monopoly should suffice. In reality it depends on how much was spent on the initial innovation. One tricky issue is also the lead time to market. In the synthesis example, Yamaha came out with a synth within ~2 years of licensing the patent. But in some areas (like medicine) it can be common for it to take 5-10 years for a product to come out, in which case a 5-year patent would be worthless, because it would expire before you can sell anything.