Can you tell me more about it ?
I have an instance variable where I can type the name of a function to be called when I click the button. And another for function parameters. Makes it easy to set up everything without having to specifically have an "on button clicked" event for each button and makes it easy to use multiple instances of a button that do different things.
As for price there's two ways to do it.
Three: Forego monetary gains and release it for free. Adds to a healthy plugin ecosystem. Take a plugin, make a plugin. :)