I handload everything so have had virtually no experience with any Russian products except for some .22 ammo years ago. Some of that was trash, some of it good.
I had no idea the Russian ammo and other products were so popular with US shooters. Is is strictly price that accounts for the popularity?
Price and availability, yes; for the most part.
If your AR, for example, can shoot steel 223 without issue, and it's primarily a fun gun for plinking, it's financially smarter to shoot steel.
Lucky Gunner did a serious torture test, 10,000 rds over 2 days, trying several brands of steel, and 1 gun shot Federal brass. 1 gun dedicated to each brand.
Some reports of "problems"; the Tula gun had problems after around 5k or so, but they finished it off with another gun (not included in the tests).
Others listed some failures, but I think the number was around 16 or so (out of 10K). So, 1-2 bad rds out of a case.
They reported that the barrels were shot out on the steel-cased at the end, while the Federal gun was still fine. But they also pointed out- the difference in cost of ammo meant they had saved enough to buy more barrels and still come out ahead. And that was pre-panic prices, which were better.
In today's market, I could find 223 steel-cased ammo for around $350 a case, new brass (and it's not Federal, it's Igman or PPU) for around $500. That's $150 a case. I built my most recent cheap AR for about $400. So, 3 cases of ammo- shooting steel, I save enough to buy not just a new barrel, I could build another gun.
Not to overload this post, but there are other reasons to buy steel, too. Steel 308 (7.62 NATO), if you have an AR or a FAL it's not a big issue, one way or the other. Steel is cheaper but dirtier, and not as precise (but people were still hitting targets, so it's not awful).
But if you have a roller-delayed rifle (HK, PTR, Cetme etc), those beat the living **** out of the cases. I have a Cetme-based C308 (I know, cheap Century ****, yada yada)... sources confirm Century brought in PTR for the C308, and mine has been solid. 100% function with steel-cased. Occasional fail to eject with brass- because it has a fluted chamber, and the Armscor brass I had would occasionally expand and get stuck in the flutes. I've looked at the cases, thats what happened.
For something like 9x18 Makarov, I could occasionally find Geco or PPU brass, but those were designed around steel and the cheaper Wolf or Tula shot well.