The trouble with that is, when given the option of paying or not, the vast majority of users will choose "not," at least given a wide enough target audience (some niches may be filled with more generous people of course..)
I agree that it's hard to sell application software to individuals. But it's much easier to sell application software to businesses (including software that helps make individuals money), and to sell system software (components and tools). Business have both the money and a desire to preserve their reputation, so most will go legit even if the software's open, especially if support comes with the purchase.
So there's no reason why this sort of software shouldn't be open, particularly as such customers are the ones who are most interested in tinkering. I doubt RMS would have started GNU/FSF if that printer driver had been open source but not free of charge.