Why make the Porsche carrera GT?

Answer 1

Often times car companies make ultra high end cars to have a project to develop new technologies, which trickle down into their high production cars. They usually develop a racing version of the supercar for use as a racer, where it can be tested and molded into as best a racer as they can make. Then they take the technology from the racer, adapt it for road use and add luxuries like leather and a stereo for the supercar consumer. Then they take the technology that the supercar has and tame it a little more for mass production in high production sports cars.

in some cases, the ultra high end cars are sold at less than they cost to build, because they were designed strictly for research and development. if they were sold at production cost, they would not sell, but they like to make back as much money as they can. For example, the Bugatti Veyron costs between $8 and $10 million USD to make (depending on exchange rates and such) but was sold for between $1.2 and 1.8M in the US (depending on options and dealer markups)

in the world of luxury cars, Mercedes uses this strategy with its S class and Maybach and BMW uses it on the Rolls Royce. Many of the toys and gadgets in everyday cars were originally on one of those 3 (SatNav, seat belts, cruise control etc),