GC margins?

[Ravi P.]

We bid a renovations project to 3 GCs.  I have only received 1 response so far. But the GC accidentally sent me a breakdown of his subs cost associated with the project with his mark up 45%  plus a 5% kick back fee to the interior designers that referred him.  So I am looking at a 50% mark up.  I know the GC provides a service and deserves to be compensated for his services, so long as he earns it.  But I am curious to see what is the typical GC mark up.  My understanding is that most GCs get paid  on a cost plus method similar to this one but I am shocked by the margin of the mark up. The other 2 GCs are independent of the interior designers. 

Another issue for another day is the kick back fee to the designers. I paid them a reasonable flat fee for there services.  The fact they are pushing their contractors makes me skeptical. I felt like they were pushy, but I assumed they wanted to work with people they know.  But I now know the real reason.  They fee they would have made on the kick back would have doubled their income.  

What I really want to know is what is a typical GC fee.  The renovation project should cost about 100k.