I think the key here is 'what is a good honey crop'. The national average, last I heard, was around 30lbs per hive (I'd estimate this at 1.5 supers if National). Obviously some will be better, some will be worse.
For bee farmers, this figure is usually significantly higher. As a student on placement with the NBU I heard figures of 100+lbs a hive being mentioned as not unusual for UK bee farmers.
As I understand it, bee farmers are more likely to have larger colonies than hobbyists although there will be other factors too.
An observation, not aimed at anyone - In my experience, for anything in life where the comparison can be drawn, there are good and bad hobbyists and good and bad professionals. A good hobbyist is often better than a good professional. However the average professional is usually better than the average hobbyist.