Apple's App Store does have costs associated with uploading apps to the store. However, the way these costs work might surprise you. There are several costs that you may need to take into consideration, aside from the costs that come with making the app itself:

• You'll need to pay $99/year to join the App Developer group. Apple made this mandatory and actually, it comes with some nice benefits that can help you streamline your iOS app programming. 
• You may have to rework certain parts of your app to keep it in line with Apple's community guidelines. This can cost nothing, or a bunch, depending on the way that you got your app made.