I've been maintaining this list on the xbox360achievements.org forums, figured it would be a help here too.
5 Most Expensive Cars
- 1964 Ferrari 250 GTO - 10,000,000
- 1967 Ferrari 330 P4 - 9,000,000 (Player Level 30 Reward Car)
- 1957 Ferrari 250 TR - 8,000,000
- 1965 Shelby Cobra Daytona - 5,000,000 (Player Level 30 Reward Car)
- 1958 Aston Martin DBR1 - 6,000,000
Disc 1 Ferrari's
- 1969 Dino 264 GT - 55,000
- 1957 250 California - 3,000,000
- 1957 250 TR - 8,000,000
- 1968 365 GTB/4 - 270,000 (Player Level 16 Reward Car)
- 1964 250GTO - 10,000,000
- 1991 512 TR - 75,000
- 2009 California - 220,000
- 1984 GTO - 320,000 (Player Level 25 Reward Car)
- 1999 360 Modena 90,000
- 1967 330 P4 - 9,000,000 (Player Level 30 Reward Car)
- 2004 F430 - 150,000 (Player Level 28 Reward Car)
- 1987 F40 - 380,000
- 1995 F50 - 400,000 (Player Level 31 Reward Car)
- 2006 599 GTB Fiorano - 310,000
- 2011 FF - 280,000
- 2010 458 Italia - 240,000 (Player Level 34 Reward Car OR FM3 Profile Import)
- 2011 599 GTO - 370,000 (Player Level 36 Reward Car)
- 2002 Enzo - 1,300,000
- 2010 #89 F430GT - 1,000,000
- 2010 #83 F430GT - 1,000,000 (Player Level 38 Reward Car)
- 2010 599XX - 1,500,000
- 1998 #12 Risi F333 - 2,200,000
Level 1 - Sport Supermini
- 2008 Toyota Yaris S - 10,000
- 2009 Ford Fiesta Zetec S - 19,000
- 2011 Suzuki SX4 Sportback - 14,000
- 2010 FIAT Punto Evo SPORT - 20,000
- 2011 Mazda 2 - 14,000
- 2009 Honda Fit Sport - 12,000
- 2009 Scion xD - 11,000
Level 2 - Ready To Tune
- 1992 Volkswagen Golf GTi 16v Mk2 - 6,000
- 1989 Toyota MR2 SC - 6,000
- 1994 Mazda MX-5 Miata - 7,000
- 1994 Nissan 240SX SE - 7,000
- 1994 Honda Civic 1.5 VTi - 5,000
Level 3 - Classic Sport Coupe
- 1969 Nissan Fairlady Z 432 - 12,000
- 1965 Alfa Romeo Giulia Sprint GTA Stradale - 60,000
- 1973 BMW 2002 Turbo - 28,000
- 1971 Nissan Skyline 2000GT-R - 28,000
- 1971 Lotus Elan Sprint - 30,000
Level 4 - Compact Hot Hatch
- 2009 SEAT Ibiza CUPRA - 17,000
- 2009 Renault Twingo Renault Sport Cup - 16,000
- 2008 Alfa Romeo MiTo - 20,000
- 2011 Citroen DS3 - 24,000
- 2010 Mitsubishi Colt Ralliart - 22,000
Level 5 - Friday Night Cruiser
- 1960 Chevrolet Corvette - 80,000
- 1957 Ford Thunderbird - 60,000
- 1965 Pontiac GTO - 44,000 (American Muscle Car Pack)
- 1966 Chevrolet Nova SS - 78,000 (American Muscle Car Pack)
- 1965 Ford Mustang Coupe - 26,000 (Ship Bonus Car Pack)
Level 6 - Trans-Am Legend
- 1970 Mercury Cougar Eliminator - 48,000
- 1969 Pontiac Firebird Trans Am - 45,000
- 1970 Ford Mustang Boss 429 - 120,000
- 1969 Chevrolet Camaro Z28 - 45,000
- 1971 AMC Javelin-AMX - 20,000
Level 7 - Early Drifter
- 1988 Mitsubishi Starion ESI-R - 5,000
- 1985 Toyota Sprinter Trueno GT Apex - 6,000
- 1992 Nissan Silvia CLUB K's - 6,000
Level 8 - King of the Road
- 1971 Ford Mustang Mach 1 - 40,000
- 1973 Ford XB Falcon GT - 50,000
- 1969 Shelby GT500 428CJ - 110,000 (American Muscle Car Pack)
Level 9 - True American Muscle
- 1969 Oldsmobile Hurst/Olds 442 - 40,000
- 1970 Chevrolet Chevelle SS-454 - 48,000
- 1969 Pontiac GTO Judge - 44,000
- 1970 Dodge Coronet Super Bee - 250,000 (American Muscle Car Pack)
- 1971 Plymouth GTX 426 Hemi - 125,000 (American Muscle Car Pack)
Level 10 - Fresh Design
- 2010 Peugeot RCZ - 34,000
- 2009 Volkswagen Scirocco GT - 32,000
- 2010 Mazda Mazdaspeed 3 - 17,000
- 2011 Mini Cooper Works Clubman - 30,000 (Walmart Pre-Order)
- 2011 Alfa Romeo Guilietta - 36,000 (Game Stop Pre-Order)
Level 11 - Historic Rally Icon
- 1980 Renault 5 Turbo - 38,000
- 1992 Ford Escort RS Cosworth - 24,000
- 1992 Lancia Delta Integrale EVO - 22,000
- 1994 Toyota Celica GT-Four ST205 - 9,000
- 1982 Lancia 037 Stradale - 240,000
Level 12 - Early Touring Car
- 1987 Ford Sierra Cosworth RS500 - 52,000
- 1991 BMW M3 - 16,000
- 1990 Mercedes-Benz 190E 2.5-16 Evolution II - 26,000
Level 13 - Sport Off Roader
- 2008 Volkswagen Touareg R50 - 65,000
- 2008 Land Rover Rage Rover Supercharged - 68,000
- 2009 Audi Q7 V12 TDI - 100,000
- 2009 Jeep Grand Cherokee SRT8 - 36,000
- 2006 Dodge Ram SRT10 - 24,000
Level 14 - Advance Tuner
- 1995 Toyota MR2 GT - 7,000
- 1995 Mitsubishi Eclipse GSX - 6,000
- 2000 Honda Integra Type-R - 8,000
- 2000 Nissan Silvia Spec-R - 16,000
- 1997 Honda Civic Type R - 9,000
Level 15 - American Drag Racer
- 1971 Plymouth Cuda 426 HEMI - 120,000
- 1967 Chevrolet Corvette Stingray 427 - 90,000
- 1967 Dodge Coronet W023 - 180,000 (American Muscle Car Pack)
- 1968 Dart Hemi Super Stock - 350,000 (American Muscle Car Pack)
- 1964 Ford Fairlain Thunderbolt - 200,000 (American Muscle Car Pack)