You should not underestimate the creative side either. In my advertising agency we charge around $250/h per person and it takes time to come up with something good, and there are often big work groups. Then, as you say, you have to change everything from pens and envelopes to signs and stripe cars, planes and so on. The worst thing is when some really big companies change their logo at an enormous cost and the new logo sucks big time. Just that happened here in Sweden some time ago when a bank changed their logo from a classy, trustworthy logo to a logo that looks dated back to 1998 and definately won´t be "right" in the near future.