They get charged $1000 (by me) if they go over time. You have to realize they don't do appliances or landscaping, this is a build on your site type situation. My SQ FT numbers came back and I paid $76.67/finished sq foot.
I have been in London since the day after I moved in but my wife is loving it.
Some unique features include 3 car garage with 14 foot ceilings (lift much?), 10 foot downstairs, 42" cabinets in the kitchen, 10 foot basement height, laundry is off the master suite (you take your clothes off in your room, you put them on in your room heck I now wash them there). I am really impressed with the builder and I especially like the way I could change things to make them my way.