@comp9 He usually just says: "Buy something, will ya?"

This is an Easter Egg if you have the soapstone when you talk to him, which is somewhat of a pain to do.

I couldn't find anyone quoting what he actually said, just people mentioning that he says something different. So when I did it, I posted the screenshot in case anyone else wants to see the message without doing the work.

That's interesting, it seems short. What does the shopkeeper typically say with other items?