The site cost actually has me worried because although it said fixed, there were 3 things that would make it go up (so not really fixed). Something like if they had to use screwpiles for our foundation, if the engineer's report from the land agent would turn out to be different and I forgot the last one...
Our salesguy did say that it was very unlikely to happen and I confirmed with the land agent as well!
So many "hidden" costs along the way, I reckon.