It's an oversimplification but as far I understand it's not wrong at least with past/current projects.
Efficiency for a given aircraft is nice but it's not the point. I believe Concord was most efficient at cruising speed (~Mach 2) but it does not change the fact that it burned like 4x more per seat/km than a b737 (Cf: https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft). Of course Concorde was only first class but that's part of the point of the parent.
As for boom, some guesstimate are around at least 4x too (https://theicct.org/new-supersonic-transport-aircraft-fuel-b...). No idea how biased this is but I believe it's quite telling that there is only mention of SAF on https://boomsupersonic.com/sustainability. At best in some 2017 article they compare themself to a lay-flat bed in subsonic business class, but since they only manage to secure an engine maker last year it was firmly in the guesstimate too.
Efficiency for a given aircraft is nice but it's not the point. I believe Concord was most efficient at cruising speed (~Mach 2) but it does not change the fact that it burned like 4x more per seat/km than a b737 (Cf: https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft). Of course Concorde was only first class but that's part of the point of the parent.
As for boom, some guesstimate are around at least 4x too (https://theicct.org/new-supersonic-transport-aircraft-fuel-b...). No idea how biased this is but I believe it's quite telling that there is only mention of SAF on https://boomsupersonic.com/sustainability. At best in some 2017 article they compare themself to a lay-flat bed in subsonic business class, but since they only manage to secure an engine maker last year it was firmly in the guesstimate too.