It depends on the house. Most likely they may have gotten past a construction deadline whereby they had to make upgrade choices (i.e. flooring). The increase in pricing is likely the cost of the flooring they added. I heard a story about someone that walked into the Bay Collection and negotiated $120K off the asking price, $40K for a landscapin allowance and $15K credit if they use Standard Pacifics in house lender. The key is the house has to be ready for occupancy with 30 to 45 days. Builders do not want to hold onto standing inventory.
Negotiate every thing you can. Dont be afraid to walk out the door and leave your number.