Please can you help value him?

[be positive]

the problem is (potential physical causes aside) those of us on livery may struggle to find a yard that will accept a cribber or windsucker. That reduces the market for them even if it's an otherwise good horse.
I know my YO would have a fit if someone bought a horse that did either.
He's still of the old fashioned belief that vices are "catching".

I took on a cribber short term, fortunately, I had no concerns about others picking it up, not too bothered about the damage to the metal strip on the top of the door but the constant noise that seemed to follow me around the yard drove me mad.

I do think it is linked to ulcers, when my own horse was on box rest, had been on loads of drugs, had a traumatic time in hospital, started cribbing one morning while I was watching him he had a look of bliss on his face when he took in the air, my reaction was one of horror, I was straight onto the vets and he was on GG within a few hours of me seeing the first gulp, he stopped straight away and has never shown signs again so I suspect he had ulcers and the cribbing gave him relief.