According to the article they are charging 19 yuen for something that costs (presumably at scale) 60 yuen and have no real way to ensure they don't get stolen this way. Not sure what they really expect :\
The reason it failed is because of this simple use case:
You want to return it just after you arrived, and it is still raining outside (this is why you rent an umbrella in the first place). If you wait for the sky to be clear to go out, you won't remember the umbrella. But if it is raining again when you go out, why would you want to return the umbrella???
Regardless of what the credit card statement or receipt says, you pay 20 yuens and get to keep an umbrella, so "price" is the right description.