Estimates for custom home building

I am planning to build a home with the cost+ model and am in the process of getting estimates with several builders. What I see is an average of 17-19% commission for the builder on top of the cost. Is this a good price for Raleigh area in North Carolina?

It's a real mixed bag and 17-19% on top of what costs (retail or builders actual costs, etc.)? And will your builder take the incentive to up charge items because the more they spend, the more they make or will they be fair?
Search "cost plus" here and you'll find a few threads on the subject but not a lot of meat. There may be a few good construction books that will give you some insight. A finance officer or lawyer that is experienced in such contracts can give you some feedback on your local "rate".
___________________________
San Diego handicap ADA Bathtubs remodeler