I would like to estimate the initial cost that I would need to afford in order to create an application that runs on the major mobile platforms. Let's assume I can do the design&code in my free time (which is also called night somewhere around) and I already have all the devices I need for staging. The app must run offline.
Another "requirement" is that the code is as most reusable as possible between platforms. A reasonable choice could be MonoTouch, since you can code for WM6, WP7, iOS and Android in C#, but I found it costs 400$ for each platform
AFAIK, Google and Apple retain 30% from your sales. AFAIK, again, Microsoft wants 99$/yr subscription and I don't know how much does they retain from sales.
Could you illustrate me the complete prices/policies for developers of the three overmentioned platforms? I already have Visual Studio and I don't know if there are alternative tools to code for iOS/Android with the same language than MonoTouch.
Finally, I should try to obtain a ROI from all this. The higher the initial costs, the farther the objective and the higher the risk.
Thank you in advance.
[Add] Just for completeness: that cost equals to 0€, 0$, 0BTC (whatever) for desktop platforms since Java is free and widely available, and Eclipse is open source; or because .NET runtime is free, and both MonoDevelop and Mono rumtime are open source
There're other alternatives too, such as PhoneGap and Titanium, both works on multiple platform and uses HTML5 for development. I've never used any of them, but acc. to my colleagues both are free to use. Apple charges $99/yr. for developer account and Android charges a $25 one time fee. However Apple needs paid developer account for even the testing on actual device, while Android allow this for free. So if you plan to distribute the app through other means than android market premium account is not required for Android.