I don't see that at all. Unless you are just building free throwaway apps in your spare time, it's in the realm of reason for any serious app.

People do make decisions based on icons, so a better icon can be good investment if you are trying to attract downloads.

In the Apple ecosystem, you need a commitment to good design. It's less strong than it used to be (for example read John Siracusa and early Gruber criticising Apple's design choices with in OSX or Pierre Igot taking every app he comes across to task). But it's always been a defining point of playing in the Apple world, ever since Steve Jobs mentioned his calligraphy classes.