The link below is a report which will answer your question. It's a long read but will convince you to never use steel case ammo.
Barrel erosion was the main concern with steel cased ammo. Other than short stroking issues with the Tula ammo which was blamed on propellent.
Barrel erosion was caused by projectile, not case.
After reading everything I think the cost/benefit of the steel cased ammo was at least even, if not greater than brass.
I believe, based on the test, that properly loaded steel cased ammo from one of our ammo plants would be equal to, or extremely close to brass.
And for plinking in my AR’s the cost outweighs, by a long shot, any rare, very rare, malfunctions.