If there is any noticable wear on the cam then it is shot. The cam is surface hardened and once any material is removed that surface is gone. Once gone they wear incredibly quick.
The wear is both on the cam and rocker arm and will put a lot of metal into the oil. I have seen scores of cars sold with a new rocker on a bad cam and they can go 10k miles before they are rapping again. The only reason to ignore it would be to dump the car.
I would say any change of shape or lip at edge of wear would be reason to condemn. Slight surface roughness might be lived with but the rockers must be evaluated as they are what wear out first.
Bosch Master, ASE Master, L1
33 years MB technician