Right. Reducing the delta-v by a constant amount reduces the fuel requirements by a specific percentage. The correct thing to measure delta-v savings to isn't t

Right. Reducing the delta-v by a constant amount reduces the fuel requirements by a specific percentage. The correct thing to measure delta-v savings to isn't the launch requirements, but rocket exhaust speed. That is, if your rocket exhaust speed is 1 km/s, saving a km/s of delta-v will reduce your fuel requirements by a factor of 2.718