We are looking to add a master bedroom on the second floor of our home located in the Shenandoah valley. the addition would be 14 x 20 and buit on posts with the lowerlevel not enclosed. In additon to the room we would need to add a double sink in a 5 x 6 room in the corner of the addition and move a toilet in the existing house. We would also need to build about a 8 foot wall with a door in the existing house. Is $40,000 ($143 per ft^2) resonable for this additon.
Your estimate sounds like it's probably in the ballpark but you need to get some local quotes to verify that. Just wondering, why aren't you enclosing the lower level. It will certainly make the addition much harder to heat and cool with nothing underneath it. It's even noticeable in rooms built over garages in many cases. Be sure to use very good insulation in the entire room for better temperature control, I would personally use closed cell spray foam insulation, it has a much higher R-value and completely prevents air infiltration as well as acting as a vapor barrier.