I'd say 80 cents up to a dollar on every device sold for the pro version. The lite version should remain free. Both will drive more purchases for your other pro

I'd say 80 cents up to a dollar on every device sold for the pro version. The lite version should remain free. Both will drive more purchases for your other pro products. It would be better if you could bill the manufacturer for the number of devices produced, just like Microsoft did with DOS. Otherwise you could count only on customers' willingness to upgrade the software to the pro version. The shareware model of reducing functionality after x number of days would motivate them to upgrade.