I agree that there is a possibility the quality is still good enough he might be able to get by. I have some customers who won't accept the smallest defect in a print and others who will print with 50% of nozzles missing. Everyone has a point where they won't sell it anymore.I'm going to disagree. Other than soaking the head to see if it cleans up, I wouldn't even think of a head replacement with that degree of wear - assuming your prints still look good.
Blacks always degrade first and that doesn't look too bad. Just adjust your print profile to compensate and you should be good to go.
Beats spending $3K on a head and you probably can get a near perfect print out of that one with a bit of profile adjustment.