The pricing of the cars in the garage is all over the place, a Corvette Z06 costs 100,000 Wp, but its Cadillac-badged sister, the XLR-V costs a paltry 5,000 Wp. Also in what universe does a Volkswagen Scirocco cost 15 TIMES MORE than a brand new Cadillac Escalade? Cadillacs really seem to be the least expensive cars in the game. Also why are the Nissans all so expensive? For the 15,000 WP you'd pay to get a Nissan 370Z, you could buy a Cadillac XLR-V, Cadillac Escalade, Ford Crown Victoria, Dodge Monaco, Pontiac Solstice GXP, Pontiac Trans Am, and a Dodge Charger SRT8 and still have enough left over to get 2 or 3 more cars. There just doesn't seem to be any logic to it at all.
Even more, the McLaren MP4-12C is just a bit slower than the F1 but the F1 costs a whopping 750,000 WP while the MP4-12C is reasonably cheaper. Moreso, the Pagani Zonda Cinque is priced at a huge 1,000,000 while being at the same performance level of the F1.
The Ford Shelby GT500 is reasonably easy to unlock in a challenge, a lower performance 1968 Mustang Fastback, however, has a challenge that's incredibly more difficult to finish.
Chances are, they might have been trying to base the car prices in WP off of how they are priced in real life. The Corvette, Ford GT, Mustangs and other "pony cars" are reasonably cheap American cars. However, cars of other nationalities such as an English McLaren F1 and Italian Pagani Zonda Cinque cost a lot more.