You can charge for your services based on a variety of items like the raw storage used, storage reliability, accessibility and so forth. The main question is what customers want to have. Make it easy for them to understand what they get and what they have to pay for it.
From a business perspective it's important to charge for your service in a way that reflects the cost of providing this service as close as possible. It simply makes calculating and controlling your price easier.
Complex pricing systems put an additional effort on you and your customers and increase the processing cost and time. Keep the KISS approach (Keep It Stupid and Simple) in mind, because complexity shows up early enough.
Use measurable Service Level Agreements (SLAs) and keep them simple and clear. The more pitfalls and perceived pitfalls they have the more you will have to negotiate and cope with your customers. Lawyers might love complex contracts, but customers don't.
This was first published in September 2003