Tell him you'll keep it at your shop and sell it on consignment. I have some cabinets here that just won't sell.... mainly because the ex-customer has too much sentimental attachment to it and thinks it's worth more than it is.
About a year ago, I had a cabinet 3' x 12' one sided. I told the potential customer I had a used one that size and called the ex-owner of it only to find out he had passed away about 12 years ago. [That's how long it sat in our shop.]
Told the guy, he's in luck. Only $500 for the entire can..... 'AS IS', and pay for the decoration of the face and it's his. Well, he had us re-wired it, new ballasts, sockets the whole nine yards and we got $2,300 without installation. He was happy. A new one was like $3,200.
I wouldn't give you a dime for it, but I'll try to sell it.