I found there are a few type of people willing to buy apps in google play in my circle of friends.
First of all, they are local australian , not Hong Kong people. They are happy to spend some money in good app. Most of Hong Kong people are still thinking android apps have to be free. Well ,there is no free lunch in the world.
Second type is ex iphone user. They get used to buy apps in appstore. Paid app is nothing strange to them.
Third one is business users. If they will buy any app which can increase their productive or earn money, they are very willing to buy those apps.

If you want to build some paid, you can target those kind of people