What's really weird is that people park their car somewhere and pay 8 Euro parking fee without thinking about it. But when an app (which sure lasts a lot longer then a couple of hours of parking space) costs any amount more then zero people it suddenly becomes a mental barrier for people...
Threema would need to switch to an in-app purchase model in order to be able to handle "gifted/sponsored apps" manually, but then people would probably be pissed because "the app looks free but then requests a payment".
The Android version can also be obtained (and gifted) through https://shop.threema.ch/, but this requires manually installing an APK. The best way would be for Google to provide a means to gift apps to others in the Play store. I really can't comprehend why they don't do this.
I paid for Threema this month while looking for WA alternatives. I had to pay the money just to find out that absolutely nobody in my contacts uses Threema.
Was it a waste of money? Maybe, but I'm ok with being the first, most people would not be ok with that and I have a very real concern I'll never see a friend join me there, then it would be money wasted.
WhatsApp charged its users to continue using it after a year, I wish Threema took this approach. I paid that money without issue because I already saw the value, so did a lot of people I know. So it's clearly not that people won't pay, but they need to show their customers it's worth it first.
Mobile phones apart from the device itself are seen as free. Your conditioned to expect to get apps for free, I expect content to be free.
So when you start asking for money; there is no association between the price wanted and a physical object. Only an application which was free.
And yes you could say that the same people won't bat an eye spending 4 bucks on beer, but beer is an immediate reward in itself. The brain is usually already wired to automatically reward it's own decision to buy beer and buying one beer lessens the very restraints that would stand in the way of buying beer to begin with.
These factors are usually not present when buying an app, unless it's a game or similar or it becomes a "passion" purchase.
I don't know how to fix this. I would like to blame Ad Tech and the blight of "free" apps that fund themselves out of mining people's data. I think it is fair to say that this was a contributing factor at least. At the same time, I think there is genuine value in a proposition where people can pick to get the product for "free" and sell their data, or pay for the product and keep their data private.