Certain parts of the RE are a bubble. Development of raw land, however, is NOT.
Real estate booms and busts have ALWAYS been regional, what we are seeing now is a nationwide boom. Certainly there will be some dips in certain regions, but it will not be nationwide. Even if interest rates go up 2 or 3 percent, they will still be a bargain compared to a generation ago. And you are correct, there is a finite amount of raw land left for development, and it will ALWAYS be a sound investment.
Unless you take inflated construction costs into consideration....in our area, those figures are over twice what they would have been even three years ago.