Futuremark published a chart that compares the price and performance of graphics cards and processors in 3DMark.
The results are somewhat surprising. It appears that the NVIDIA GeForce 8600 GT gives the most bang per buck, per dollar you get 56 3DMarks with card. On the second spot is the Radeon HD 3850 with 54 3DMarks per dollar and the GeForce 8800 GT is third with 48 3DMarks per dollar. Other popular cards like the Radeon HD 3870, GeForce 8800 GTS 512MB and GeForce 8800 GT score 41, 34 and 22 3DMarks per dollar, respectively.
The quad-core segment is owned by Intel. Their Core 2 Quad Q6600 gives you 14 CPU Marks per dollar and is followed by the Core 2 Quad Q6700 and Core 2 Quad Extreme QX6850 with 7 and 5 CPU Marks per dollar, respectively.
AMD dominates the dual-core processor market with their Athlon 64 X2 lineup. The chip that gives the most bang per buck is the Athlon 64 X1 3600+ - it scores 29 CPU Marks per dollar. The top five also includes the 4000+, 4200+, 4800+ and 3800+. On the eight spot we find the first Intel CPU, a Pentium D 820 which scores 18 CPU Marks per dollar. The first Core 2 Duo processor is found on the tenth spot, the Core 2 Duo E4500 which scores 16 CPU Marks per dollar.