If your talking about the Veyron and Gran Turismo 5 you don't buy it but win it. The championship you win it in is the Gran Turismo World Cup.
here are all the prize cars that you can win in gran turismo 4 : http://guides.ign.com/guides/489327/page_7.html
Finish first in all courses
You can buy it for 1,000,000 Credits at the Online Dealership. You can also win it with a gold trophy in the Gran Turismo World Championship. Good luck
You can either win them in event tickets or purchase them from the Used Car Dealer.
The same car you win in Nurburghrr....24 hrs endurance (F1)
well for online and live.go into a open lobby.make your own.then click race.then an automatic win
If it has no price, and just shows something like "Cr. ----", then it will be unlocked as a prize. Try doing some more race events.you can get it as a prize car by completing driving missions 21-24
When you win the Historic Racing Car Cup you get the Lancia Stratos Rally Car '77, the only other way that I can think of is through the used car dealership.
Try using the Chapparal 2J. I used it and it's the beast. The car is 1 million credits, to get the money fast repeat the race in Special Conditions (the second one on Easy), sell the prize car (it's around 257000) and just repeat to get enough for the car.
just win the race
You can get bugatti Veyron if you win GT World Championship in 1st place.Buy a Ferrari 599 fully upgrade then its 90 % is that you can win good luck and try it.You must be lvl 15 because GT World Championsship in in Profesional Spec-A.