When it comes to buying the device, thousands of people line up outside Apple stores and pay - I don't know - $600 for their device.
Android devices are the same, many people easily spend ~$400-$600 on their device that they may only use for one year.
So a good chunk of mobile users are people with good income, living in rich countries and are well capable of paying $5-$10 for their apps that they run on their expensive/high-end devices.
Yet when it comes to paying for apps they struggle as if their monthly income is $10.
There are many factors involved but I think the most significant one is by far the psychological perception of the value of apps that has been created due to App store and Play store pricing.
There are also many people who are willing to release free and good-enough quality apps because it's their hobby or maybe they want to create a portfolio for themselves.
This reduces the perceived value of these apps.
In contrast people can't find other professional services/tools for free. I mean, say, lawyers, doctors, accountants, electrical engineers, etc... don't produce and provide their services/work for free where you can download a free health checkup from a doctor whose hobby is being a doctor.
So the perceived value remains high.
Software engineers are unique in this regard because they 'discount' their work constantly and justify it by saying 'i love doing this'.