Creating a program requires hundreds of man hours. It is necessary to carefully consider the functionality of the application, take into account the variety of gadgets on which it will be launched and a number of other small, but very important details. As a result, the application receives a very complex structure, which only a team of experienced specialists can qualitatively implement.
It takes at least 300 hours to develop the simplest application designed to run on one platform. But if the program will work on devices with different platforms, the task is many times more complicated. It is also worth remembering that gadgets running Android stop receiving system updates 1-2 years after the release.