The idea that economic growth being slightly slower than it otherwise would've been is a great tragedy seems like a typical economist's fiction. It tells us very little about whether or not they'll be able to keep on manufacturing artillery shells. So long as the world is eager to buy Russian oil and gas it's hard to imagine they won't have sufficient money to keep up the killing.

That they're losing so many people seems more likely to prove unsustainable first. Perhaps they'll eventually run out of young men who can be coerced into aiming the guns they're given in the intended direction.