You make the fatal but tragically common mistake of assuming that if somebody thinks a program is worth $0.00, they would think it would also be worth $[however much it legally costs] if getting it for free was not an option.

I see what you're getting at, and I think that those piracy rates are at best accurate and at worst much higher. And as a game dev I would like to see more people paying for the software I work on.

However, there's absolutely no reason to suspect that SOPA will make a significant dent in piracy rates. On the contrary, as well as making little piracy impact, the industry will become increasingly constrained and there will be greater risk for developers.