These attacks happen all the time. The latest was two or three days ago.
The Pentagon shrugs them off. Even when 100 tankers were destroyed in 9 days in October 2010, the Pentagon said it was insignificant. I'm guessing each tanker holds about 4000 gallons of refined fuel. That would be $16,000 a truck of fuel lost, or $1,600,000 in fuel, in US retail pricing. Reality is, it costs over $25 a gallon to get a gallon of gasoline into Afghanistan, so it was more like $10,000,000 worth of fuel destroyed in 9 days.
However, with cost-plus contracting, defense contractors just see that as $500,000 profit.