One thing we don't know about is how many bathrooms, where they're located and if they are attached, etc.
As others have mentioned I think it depends on where the bedrooms and baths are located. Two bedrooms down with two full baths down seem to have good demand either for multi-generational families living in the same home, or parents wanting smaller children on the same floor. I'm also with the agent who asks why it would cost more to build, (unless you are adding a bathroom). If everything is the same, but you are just combining two rooms into one, it should be less. One less wall, one less door, etc and that should cost less. One less wall should not take any kind of architectural redesign. Anyway, good question and make sure you use a realtor during your purchase. Every day we get questions about how the builders screwed up this or that and how can they fix it now. It's always a good idea to take a realtor with you on every visit to the builder and especially the first time. If you haven't signed a contract yet, now is a good time to enlist help. For a whole list of common issues we have seen with builders see me website at http://www.teamlynn.com
and click on the new home link. No need to go at this alone, have someone fighting for you in your corner at typically no cost to you.