I understand you need to do what you can to close the deal.
It'll drive me up the wall, if someone is making a $40k purchase and complain about a set of center caps. Nevermind how much they're worth and he could buy the car and swap them later. I know it's a buyer's market but he/she should be glad you're doing this for him as a favor. That's anal-retentive and I consider myself pretty anal.