Much like the 40 S&W I recently posted about, it looks like Centerfire Systems is offering up grab bags of 7.62x.39. It's a bag of 500 rounds for $170 shipped. At this price, it comes out to about 34 cents a round or $6.8 per box of 20. The lowest price currently on ammoseek is at about 33.7 cents per round, but that's before shipping and you can only order about 200 rounds. The next lowest price has it at 36.7 cents per round plus shipping.
If it's anything like the 40S&W grab bag I got, it'll be all loose, all mixed, and possibly not very shiny, though the image they provide looks like it was all steel cased anyway, and for our regular SKS workhorses, few of us really shoot nice shiny brass stuff anyway. I've no idea where they're getting this stuff but it's still the best deal out there right now.
I actually felt kind of sad writing that last sentence as I still remember the days of $100 for 1K of ammo, but those days are long gone I'm afraid. Anyway, here's the link.
https://centerfiresystems.com/product/7.62x39mm-500rd-grab-bag-loose-bulk-packed-mixed-ammunition-copy#product_detail