About the cheapest I've been able to buy PMags is around $9 a magazine. That's a good price.
About the cheapest I've been able to buy the D&H magazines from PSA is $7 a magazine.
I'm out now (meaning I've given a bunch to the kids the last few years as we built them AR15 carbines, rifles, pistols and I don't have a reserve in one or more boxes in the garage anymore.
Oh, I have been buying the PMag 40 round magazine, only 5 or 6 so far, for the road trip carbine. The fit fine in the rifle case mag. pockets and if I really need that carbine then 40 rounds is better than 30 is better than 20 is better than 10, etc. No issues, so far, with the PMag 40's either. Forgot about those in the first post/response.