So what does it depend on? In a standard arcade or car wash scenario, is it regarded as a form of payment?

There is a real question behind your academic question. I am not running a law school class. Is your question about barter? Is this a homework assignment. What is the legal issue afftecting your life?

No, it's not a homework assignment. I'm going through Google's policies that apply to mobile apps. One of the clauses says:

"Developers offering additional content, services or functionality within an application downloaded from Google Play must use Google Play's payment system as the method of payment..."

So I wonder whether if the user can redeem tokens for 'additional content', according to the policy. It seems that if such an exchange isn't seen as a form of payment, then it wouldn't fall within the clause; and thus, no need for Google Play's payment system.

I think you need to put together a very sizable litigation budget for the the litigation with Google. Your additional facts finally made your question comprehensible.