Remember when you make a pricing model for your company: you can never change it without some kind of backlash unless you can make things cheaper. So it's fine to charge a bit more initially and figure things out as you go, you can then lower the price once you've worked the numbers and/or have to respond to competitive pressure.

But changing your model will upset your customers, no matter how well you intend it and there will always be a backlash, especially from developers for tools because there is always going to be someone else that does it cheaper. Rely on the 'cost too switch' once too often and you will shed users and users that leave will never come back. It is easier to attract a new user than it is to get someone that got burned to return.

Do what you can to get it right the first time and build in some room. And if you do have to change it be willing to grandfather in the users that got you there for ever.