The 9.7" LCD display is the most expensive part at $127, since it is thinner and better than the $95 screen on the first iPad.
Next come the 32GB memory chip at $35, and Apple's new dual-core A5 processor costs only $14, since Cupertino owns the intellectual property over its design, and uses the manufacturer only as a foundry.
The battery costs $25, and, as is usual for Apple, the company has pushed the battery maker to create a tailored solution for the specific design chosen. It is very thin, with three cells instead of the two in its predecessor, and has state-of-the-art power management, which has always been a strong point in Apple's gadgets designs.
The cost of the rear camera? Very good question - $4.30.