Certainly charging for upgrades with useful new and critical functionality is reasonable. But reasonableness would also price even critical functionality relat

Certainly charging for upgrades with useful new and critical functionality is reasonable. But reasonableness would also price even critical functionality relative to how hard it was to actually implement. I.e. don't hold hostage a customers' investments in a software product. Don't force customers to pay a ransom to get a simple-to-implement feature.