They shouldn't have charged you the $6. At least, TR didn't when I applied for my FID and P2Ps last year. I actually asked them about it because all I paid was $4 for my two P2P. I said "shouldn't it be $10," they said the $6 isn't charged because the fee for the FID is the fingerprinting cost.
Maybe TR is cutting people a break thought but I can't imagine a police department turning down the money like that.