The pro of plans from the business side is also that people pay for what they may not use. If you now have a plan that charges $40 for 400 uses and change that

The pro of plans from the business side is also that people pay for what they may not use. If you now have a plan that charges $40 for 400 uses and change that so that people pay $.10 for every single use, the revenue will simply be a lot lower - because these people may use 200 or 300, and if they were planning to really use around 400 they'd probably get a plan that offers them more to ensure they don't run out too early. So ultimately you'll need to charge quite a bit more per use if they only pay what they really use.