As an API consumer that is paying for the use of an API, I want to have a clear view of what is my current consumption in terms of money.

To calculate variable costs, price rules should be applied according to the current number of calls/units, knowing that later on that could change. For example, given the following price rules:

If current API consumption is 8 hits, I would expect to see:

If later on API consumption goes to 14 hits, then I would see:

To calculate fixed costs, a pro-rated value according to the passed days of the month should be used.

As an API Provider I want to see an estimate of the earnings up-to-date (knowing that depending on the price rules it can be more/less later on)