Actually this is inaccurate. You're off by a factor of roughly 2. The SR burns 21,000 lbs/hr per side. As a former FA-18 SuperHornet pilot and a current airline pilot - I can provide a little context.
To do an apples to apples comparison you need not only speed and fuel flow but also weight. At 0.85M and at mid fuel weight of 42K - a FA-18E will burn about 5600 lbs per hour total fuel flow. A mid weight SR-71 weighs about 105K - or 2.5x a much. If we were able to scale up the Super Hornet to the Blackbirds weight - all other things being the same - it would be burning about 14,000lbs/hr. at 510KTAS or 27.5lbs per NM. A SR-71 is burning 42,000lbs/hr at 1850KTA = 22.7lbs per NM. Therefor a SR-71 at cruise in afterburner is 17% more efficient than our scaled up Hornet flying in non AB. That in itself is pretty amazing. By Comparison, a Boeing 777 (what I fly) - at a mid cruise of .83M and weight of 550,000lbs is doing about 500KTAS and is burning about 13,500lbs fuel. If we scaled it down to the size of a SR - that would equate to a fuel flow of 2600lbs/hr or 5.2lbs/NM. This would make the scaled down B777 burning only 19% of what a Hornet or 5x more efficient - and only 23% of what a SR-71 or 4.3x more efficient in apples to apples comparison. Without doing the math - my guess is that a B737-800 would be somewhere about 25-26% or 3.9x more efficient of the fuel burn of the SR71.
I will share a different tidbit. I once flew with the commander of the last HABU squadron at Beal. This was a 3 day trip we did together where I got to share the cockpit with a guy who knew everything about the SR. As a buff I got to pick his brain - here are a few things he told me:
- Very temperature sensitive. A temperature forecast that was 5 degrees off - could mean a difference in 10K fuel.
- Would take off - maintain 450KIAS in the climb until getting to critical Mach and EAS. Passing about about 60K feet - the airspeed would bleed off until it was in the in the 410-420KIAS range which in the high 70's/low80's works out to be be 3.2M.
- The aircraft was temperature limited not airspeed limited. The aircraft got stronger and more efficient as speed increased - but the aircraft structure and engine inlets could not handle the heat. It would still be accelerating strong and they would have to pull it back at 3.2. I asked him how fast it would go if there were no temp limit - he said "Don't know - definitely 3.5 - maybe 4 - but they plane would melt before you got there". He did say - that during the Lybia raid - they got shot at by a large SAM - pushed it up - and he guessed they were doing over 3.3M when they pulled it back after defeating the missile.
- Stable airplane - flew nice - but you had to plan everything so as not to overshoot - or get down early and burn too much gas.
- He used to heat his Lean Cuisine by putting it on the glare shield under the window. Said that was about 450F. Perfect oven.
- Biggest emergency would be an "Unstart". If it happened at altitude would be an automatic ejection and probable death.
- Overall said it was a fantastic experience. Best part was the quality of the guys in the program.
