No body is going to give you an honest answer to that question.
And giving the answer in a direct and complete way could cost the person giving the information there Adsense account.
From what I hear if you had that many "quality" hubs and they are all drawing 1000 visitors from outside hubpages a month you can be making at least $3000 per month.
But most people with 600 hubs might be doing well if 60 of those were drawing over 1000 real visitors a month. That means most likely those 60 good hubs are making them $300 - $400 per month, just from the Adsense program.
As to how much those hubs would pull from the Hubpage Ad program, I have no idea.