From the day shopping started happening online, there have been retractors saying that the offline feel can never be replicated. But over time, online shopping has only increased and technology has reached to a point where the experience is getting better by the day. There have been different ways to make users comfortable and this has been different for different geographies. Mobile and apps have now hit the world in a big way and purchasing apps is a part of life for an average westerner. The penetration is deepening in developing markets as well as people start getting comfortable with the idea of paying for apps.
Google always allowed to return a paid app but the time window hasn't been confirmed. There is an official announcement now that reads:
After purchasing an app or game on Google Play, you can return it within two hours for a full refund.
How to do this on your device?
This move puts a lot of focus on quality and the user knows that s/he's be paying only for the apps they value. Apple doesn't advertise or doesn't say that it supports returns but they do refund in case of genuine cases.
Read the official announcement on Google's support page here.