Yes, someone (M2dude, I think) says that 65% of the thrust, at speed, was provided by the intakes. That said, at lower speed, all that work to bring air up to s

Yes, someone (M2dude, I think) says that 65% of the thrust, at speed, was provided by the intakes. That said, at lower speed, all that work to bring air up to speed is accelerating the plane as well. Even so, since drag tends to increase as the square of velocity, and in proportion with density -- you're spending a lot more effort to maintain velocity at higher speeds. The afterburners are mentioned as increasing fuel consumption by 80% and power output by 17%. The high fuel consumption comes down to the plane accelerating, climbing, being in denser and warmer air, and heavier -- all at once. While the engines might be marginally more efficient in some sense at high speed, this would be cancelled out by the vastly higher drag at low altitude/speed.