Dubai's 1,312 feet of megalomania - When will the race for the world's tallest skyscraper end?

From “Der Spiegel”: The world’s tallest skyscraper will open soon in Dubai, even as the emirate continues to be battered by the financial crisis. Is Burj Dubai an expression of failed megalomania or proof of Dubai leader Mohammed bin Rashid Al Maktoum’s stunning vision? The view is clear, the air is soft and silky, and only a thick strip of red separates the sky and the sea at sundown. The boundary between grandeur and kitsch becomes blurred here, halfway up the Burj Dubai, the world’s tallest tower. All of this will apply for only a little more than two weeks, until Jan. 4, 2010, the official opening date—already rescheduled several times—when the developers hope that the tower will begin serving its purpose as a magnet for a two-square-kilometer new development zone.

http://www.spiegel.de/international/world/0,1518,667262,00.html

How economic are skyscrapers? They require only small plots of lands. But the building process is more complex.

I wonder how do the efforts compare between one 400 meter and two 200 meter skyscrapers (same building area) ?

And I’ve read that there’s also a limit when the Earth’s crust can’t support the weight of a very tall skyscraper anymore. Will we ever come close to this limit?