The median will likely be 0 for almost all apps; it would be outrageously, extraordnary successful for a freemium app to convert 50% of its users to paying customers.
The mean is also uninformative - for many games the majority of revenue is provided by a small number of 'whales', and their behavior is not representative for a normal user.
Perhaps a histogram would give an accurate impression, but I'm unsure whether app devs and Apple/Google would want to make that info public.
The latest numbers I've heard is that if you get 10% of your userbase to pay at least once, you're doing incredibly healthily. Whales tend to be a handful-per-100,000 ratio, but they spend like nothing else. Loot boxes are ridiculously effective because whales will roll for them until they get the rare prize, spending thousands of dollars in the process.
The mean is also uninformative - for many games the majority of revenue is provided by a small number of 'whales', and their behavior is not representative for a normal user.
Perhaps a histogram would give an accurate impression, but I'm unsure whether app devs and Apple/Google would want to make that info public.