It's worth a thank you and lunch, or on the other hand, it's not worth insulting a friend who doesn't want to hear it. I had a similar problem with a very nice guy who had an old .22 bolt action missing a clip he wanted to sell me, who didn't and doesn't want to hear it's worth 50 bucks at best.
I decided it best to refrain from offering anything, and just tell him I'll keep an eye out for anyone who needs a .22 and pass along offers.