Not from what I can see, prices appear to have stayed similar to when the App Store was launched. However, I do find it cheaper than buying the same software elsewhere for some bizarre reason.
For example, the point and click adventure game Machinarium is £5.99 on the Mac App Store but the Steam version is £14.99. Aperture is another good example.
This seems to apply for pretty much everything apart from the games that are made by porting houses, which prices are rather higher then the CD versions it seems.