For all interested, Stroppe is correct. I just called my accountant and the appraised value of the truck is NOT deductible but, everything above the appraised value is.
In this case, if the buyer got the truck appraised at 20k, he could deduct $480,000. He could then go and sell the truck for 40k and make 20k on his appraised value.
That's how it works.
PS: If anyone thinks the person who bought it has no interest or intention on using this as a tax deduction and only cares about the cause, then they are foolish. He may care a great deal about the armed forces, but he would be foolish to not take the deduction.