Is a good deal if he thinks it is a good deal after a long test ride.
100K miles does deflate the value significantly though so if you say it is pretty cheap and get it for say 5K, go for it.
I picked up a near 80K miles 1998 honda valkyrie tourer locally for 3K not mint by any means, but most last November being 1 year ago in this age/shape were going for 4K easily. He begged me to please by it since while there talking to him he got 2 more phone calls asking questions about it and he said he had dozens of tire kickers blowing up his cell phone wanting it that first week advertised. He was asking 3300 but needed the cash soon, cash in hand talks!

always wanted a tourer with LOUD cobra exhaust and that one fit the bill regardless of miles/condition due to price so if a very good deal comes around, I say go for it before it is gone. I did the same thing with a 2008 can am max outlander 2-up ATV 800cc only 2000 miles snatched it up for 5500 bucks ASAP about 6 years or so ago most in that condition wanted 7K at the time. I could still get 5K for it now.