Why so large? What's special about iPhoto?
It is because when you edit a photo in iPhoto it saves two copies of it the original and the edited one in separate folders. incase your edit looks bad you can control click the photo and hit revert to original or show original.
543.7 if I read correctly.
Make sure you check the Photoshop folder, not just the binary. iPhoto carries its supporting goodies inside its bundle. Oh, and don't forget Bridge (since Photoshop alone really doesn't do what iPhoto does) and the Adobe folders under /Library.That's 10 times larger than Photoshop.
We arent talking about library size, unless your saying the code to enable that is alot.