Marina Bay Sands. monticello/Shutterstock Dozens of buildings across the world have crossed the billion-dollar price tag. Some of the world's most expensive are casinos and office skyscrapers, but also hospitals or homes. Total costs often reflect not just the construction costs but also real-estate values and amenities. The logistics of constructing a building can make the price tag as high as the towering tip of a skyscraper, but figuring out how much it costs to build a tower or casino isn'