How do you pay people question, incentifying work vs result

[Dan Bryskin]

I am looking at how to align my interests with my in-house general contractor. In my best interest is to get project in minimal time, for least cost and get the best product. For contractor to make most money, he wants to inflate the bid. Say I have a project, say reasonable number for labor and material is 100k. My GC wants to get a bid as high as he can, because that means more profit for him. I'd like the project to produce more profit for him if he delivers me a project at 80k, instead of 100k or 120k. To do that, I need my GC to work for the percentage of the profit, but it gets trickier as the guy needs money every week. I am curious to see what are some of the methods people here came up with, to incentify the end result vs incentifying work. Please share your thoughts, thank you.