I think that sounds more than reasonable, you might be able to shave a little more off the asking price of 2 years ago, depending on the circumstances i.e. has the builder gone bust, who now owns the house etc..
What's the current asking price and what was the peak price 2 or 3 years ago?
If the builder has gone bust, just make sure you know what the situation is regarding the estate being finished. You don't want to be living on a building site with unfinished roads, landscaping and no street lights etc..