Well, they (MS) have Xamarin, which is free, and targets Android, iOS, and WP. You could likely share a lot of the codebase with a UWP app also, since it's all .NET natively or supported (UWP supports other languages, eg. JS, C++ etc). It's a pretty compelling option, and works well in my experience.
I am one of those people who like Xamarin, especially now that it is open source. But needing a Mac for iOS is a pain. I understand it is hard to not work like that but it is annoying. That said, I do like Xamarin and currently work fast in it.