I have yet to see you tell something is not "very cost efficient" about literally any unit or ability, regardless how bad it was.
Yes, major arty looks amazing on paper, everything looks amazing on paper.
M-42 looks amazing on paper and I'm 100% positive that if someone made a topic on how bad it is, you'd be the first one screaming "how amazingly cost efficient it is for its cost and how it should never be changed".
But its a gimmick that provides muni strain and is of limited use.
Imagine you paying 60 muni every single time you want to use a panzerwerfer barrage and its max range is 50.
Barrage looks amazingly on paper, but would the unit be useful on the long run?
Same thing for major, most squishy unit in the whole game and a constant muni strain if you want to utilize him, making it impossible to save for weapon upgrades or off-maps.
Here you go again talking about me once more, I am not sure why you are obsessing with me but you should give it rest.
The ability can easily take out bunkers that cost the same munition and more manpower, clear garrison and help kill OKW trucks.
In addition the decoy/barrage can be keep the opponent guessing and relocating Soviet, Ostheer and OKW would love to such an ability available stock. In addition Major give much more.
The unit and ability is cost effective.