To spot an app that is mainly there to sell, count how many times it asks you to pay or to buy during the first five minutes.
Warning signs:
A « Go Premium » window on every screen.
A countdown: « Offer valid for 10 minutes! »
Products (supplements, devices) recommended everywhere.
Promises that are too good: « cure », « guaranteed results ».
If you see these signs: close the payment window, without touching anything else. Nothing is purchased without your confirmation.
Limitation: an app that sells is not necessarily a bad one. The warning sign is the pressure to decide quickly.
To picture it: it is like a commissioned salesperson following you down every aisle: the products may be good, but selling remains the first goal.