If I understand, you are attempting a "proves too much" argument with height, however, this is irrelevant, if height is predictive of income then this is an interesting result in itself* (maybe tall people are more respected) and has no bearing on whether IQ is also predictive of income. I agree that IQ probably doesn't scale indefinitely with success and power though. The tails are already starting to diverge at 130.

*there is a correlation