I can't give you any exact costs for an owner, but two years ago the price per hour for a G-450 on a Marquis Jet card was over $12000. Granted jet cards charge a higher price than is charged for fractional owners who are charged a higher price than what it costs someone who owns the airplane themself, but when it comes to figuring out how much it actually costs to operate an airplane you must remember that there are a million little details that go into it that don't come immediately to mind- things like insurance and hanger fees and routine mx that all add up really fast and high. The only thing I can say for sure is that it will be a gigantic favor.