If you sell a metered service, like Heroku or AWS do, are there automated ways of billing your customers' credit cards?
Normally, using any one of a number of recurring-billing options would do the trick. But it seems like these are largely intended for cases where the amount that gets spent doesn't change month-to-month.
What if the amount does change month-to-month? Are there processors or payment services that can accommodate that sort of business model?
