It really just goes back to the concept of "barriers to entry". If Apple can reproduce your software easily, they will. They might even do it better than you. They'll only go out of their way to buy you anymore when you've implemented something like Siri that's actually difficult, or something like Logic that has a massive and lucrative installed base. If you implement something trivial, don't be surprised when your competitors reimplement it instead of giving you a millions-dollar signing bonus just for your ideas.