Wachs suggested an alternative billing mechanism, one based on disk time, or the amount of time it actually takes the disk to read or write the material.

"When we charge for disk time, and chose a rate for disk time that matches the cost for the provider, the costs are being recovered fairly," Wachs said.

Attendees brought up various issues with this approach. One noted that clients may be willing to pay a bit more overall to get a more predictable and easily understandable bill, mentioning as an example how the cellular phone industry charges on a simple flat rate and per-minute basis rather than how much the actual cell phone towers are used by each customer.

Wachs countered that the disparity between the costs of running a cloud service and what is being charged can be a significant difference, and not just a subtle averaging of the costs.

Cell phone customers probably "aren't losing sleep over whether they are paying $40 a month instead of $30 a month," he said. Businesses that are paying $40 million a month rather than $30 million a month, on the other hand, may want "the accounting and pricing to be a lot closer to the actual cost," he said.