Net? Probably nothing. Boeing has lots of test flights to do just to rack up hours of operation and so forth so a flight like this easily fits into their budget of flights they have to do anyway.
747-800 burns about 2,900 gal of fuel per hour at cruise altitude and speed. This was done at 12,000 feet which probably doubled the fuel consumption. Without accounting for takeoff/climb fuel, we're looking at around 32,000 gallons of jet fuel. Cheapest fuel BFI is 5.59/gal so a good estimate for the total bill would be $178,880.00.
