Mach 4-10 Scram

A number I forgot to post in the scram success thread is maximum possible
mass gain from the jet.

From mach 4 to mach 10 is roughly 1,800 meters per second.
Mass ratio of a Lox/Kero rocket is roughly 1.7 for 1,800 m/s in vacuum.
A massless scram, that burns no fuel, and has no adverse mass
effects on the airframe or thermal system, has a minimum
possible mass of 60% of the all rocket vehicle.

This is the maximum possible savings with massive use of
fairy dust and unobtanium. If you can refute this, use numbers.