According to the US Census, the average size of a house in the US is 2,349 square feet, up almost 300 square feet from 1990. We are seeing larger homes coming into neighborhoods called Faux Chateaus [Note: Subscription] or McMansions [Note: Paid Subscription].
Its not just the size thats increasing in new construction, more amenities are being added.
This trend tends to overshadow pricing in the housing market. Larger housing skews the overall market statistics, both median sales price and average sales price, so the rise in prices would be overstated.