With Re-Sale homes, there is no COST available to use in the firuging:
The house may have been built 10-20-30 years ago, and the cost to build it would be nonesense in today's market.
No so with a new-construction: The Builder knows what it cost them to build it, and they know what margin they need to make.
You can bet that the LIST PRICE is padded a little, maybe more than a little.
But you can also bet that they will not agree to a Low-Ball offer; they can sit on it while it appreciates.
The bottom line is; What is the house worth to you? How much do you love it? How closely does it meet your needs?
Try not to be emotional about it.
Good luck and may God bless