What more amazing is that 1000 ft^3 of methane is 12 tons, you need 1900 tons (in orbit) of propellant to get to mars based on the ITS design since it's about 5 trips of the ITS tanker to refuel the ITS that goes to mars (350-380 tons per refueling).

Lets put E2E propellant requirements for the BFR/Booster and the ITS at 10 times that of the martian transfer that would put the CH4 costs of the trip to less than $6500.... At 100 times that it would be about $65,000.

That will still be much cheaper than the most fuel efficient jets we have like the A380 and the 787-9 with the fuel costs of a 15 hour flight being in the range of 150-200,000$ depending on the aircraft.