need advice

I need some advice on what to say to homeowners/customers when dealing with insurance claim payments to a general contractor. I recently settled a claim from storm damage to the insureds roof and gutters. (23 square roof and 60'gutters) the adjuster who I met at the property was great! He matched my estimate and payed over head and profit. So the rcv ends up being around $15,000. Now the problem that I have been running into is when the insured, whom I already have a contract with, says to me there's no way this roof cost 15k to replace and got two other estimates from other roofers saying they would do the work for a lot less. So now the homeowner is demanding new siding on his entire house or he's having someone else do the job for a lot less including new siding. No matter how I try to explain it to this guy he just doesn't get it! I always throw in something extra, but I'm not paying to have his house re-sided! I guess these a-holes expect me to work for free!