You've got to wonder how much Apple are paying Google to support maps on iOS....or what other kick-back (more valuable to Google than cash) there might be.
Apple clearly wanted Google maps to be relegated to an also ran.
This works for both of them - the complaints about Apple maps are undermined by the existence of Google maps for iOS, Google get to retain their position as the best maps on any platform.
I see no evidence for an exchange of money in any direction.