Money & WorkFact
Freemium: a few payers fund millions of free users.
In the freemium model the basic version is free and extras cost money. Only a small percentage of users ever pay, single-digit percentages in many services. That's enough, because digital copies cost almost nothing and free users serve as marketing, data source and network. The art lies in locking exactly the feature heavy users need.
Useful: If a free app annoys you about exactly one feature, that's deliberate.
Source: de.wikipedia.org