The reduced cost will come with JSS 3.
Although needed, a third ship is unlikely though.
I wouldn't be too surprised if we did like the Germans did between the Berlin and Bohn. Sail the ship for 5-6 years and then order the next one with improvements recommended for the overall design. Bohn was in service 10 years later and is very different internally to the Berlin. Canada used the Bohn design as the baseline. Canada even improved on it from German recommendations.
(Example is the Bohn's stores crane and clamshell doors are only on the port side. Protecteur has doors and cranes on both sides. So the ship doesn't ever have to flip just to store.)
At some point the Asterix needs to be replaced and that 2% needs to get hit somehow!
It would also create a nice age gap in supply ships. Asterix ~20 yrs old, Protecteur 11yrs old, Preserver 8ish yrs old, Provider 1 year old.