(That's for shaft engines, which a turbojet isn't, but the turboprop examples are jet engines with a gearbox and propellor mounted.) Jet engines are incredibly powerful (per unit of mass) and reliable, but I don't think they're incredibly efficient.
Perhaps I don't understand the measure (entirely possible!) but I think thrust-specific fuel consumption is a better indicator here. You need to account for the thrust required in these behemoths: replace the gas turbine engines with piston engines large enough to produce equivalent thrust and I doubt you'll retain the fuel economy.
Either way, this is an auxiliary point: the per-passenger fuel economy of airplanes is significantly higher than that of cars.
(That's for shaft engines, which a turbojet isn't, but the turboprop examples are jet engines with a gearbox and propellor mounted.) Jet engines are incredibly powerful (per unit of mass) and reliable, but I don't think they're incredibly efficient.