Its all about the routes flown, fares charged, and passenger demand. Take a CRJ flying ATL-JFK with 50 pax paying 150 bucks each. Thats $7500. Take a CL-604 flying from TEB-MIA with 4 pax paying a total of $10000. Same airplane (pretty much) but people are willing to pay much more for great service taking them where they want to go.

How about if you chartered a Saab 340 in the middle of a snowstorm Christmas Eve in Chicago where there are 5000 Passengers stranded at the ORD airport. I guarantee youll be able to find a few who will pay thousands of bucks to get home to Peoria.