A good quality affiliate manager, one who manages the entire program, manages designers, understands the industry, coordinates all affiliate tools, handles affiliate needs well, attracts solid producing affiliates, responds to their needs in a timely manner and keeps them happy, one who is able to implement ideas....a true affiliate manager who dedicates themselves to the entire program and not just one piece of the program, will make well over 100k/year.
But, as beemk said, there aren't many of them. You find one like I described above and you find a way to make him happy cuz a good affiliate manager more than pays for himself.