Personal project. Responsible for planning, UX, development, testing, deployment and promotion. Hired freelance designers and writers. Currently sold.
Made this app with Xamarin. This allowed me to reduce development costs by ~20% (estimate). Initially started developing it using Objective-C. After 4 weeks of work tried MonoTouch and rewritten Objective-C code using C#. I track my progress using Trello and thus can compare amount of time spent on the same features. During the process I found that I spend about 20% less time when I write using C# compared to Objective-C. Also this made my codebase smaller, helped me to avoid memory issues and made me more productive.
In total, even for an app of such a small size (13-15K LOC) it makes sense to spend $400 on MonoTouch.
Due to the great user experience, promoted reviews and viral effect the app got a lot of installations. Reached #1 in Netherlands and Top 3 in 20 other countries. Totally, get installed 400,000+ times both paid and free.