21 of the most expensive iPhone and iPad apps in the world

If you think $10 is too much money for an app, you won't even consider downloading anything on this list.

While the App Store is full of great apps that are inexpensive or free, there are also a handful that cost hundreds of dollars.

For some apps, like electronic textbooks and professional tools, the cost is somewhat understandable. But for others, it's completely puzzling.