Hi freelabrasil,
I don't know if you have noticed, but in the Arduino "ecosphere" hardware costs money, but software is universally free, including development tools. If you have something you think is marketable, pay particular attention to that fact! Perhaps you should bundle it with a hardware component to make a 'monetary value' component. Inflate the price by your value added for the software, and claim "ease of use" or "extended capabilities" to explain the more expensive module.
A hundred bucks seems an awful lot for Arduino software though. The main use of Arduino boards is for "do it yourself" projects.
Good luck with your venture!