The cost is about the same <$29.99 ea. However I found an ebay seller offering the genuine Ruger 2-pack 22/45 (MPN 90646) for $32 shipped free.
The Ruger manual states "The RUGER MARK IV uses the same 10-shot magazine as RUGER MARK III pistol.
"The RUGER MARK IV uses 22/45 uses MARK IV 22/45 magazines only."
"Only use correct RUGER magazines for Ruger MARK IV pistols in order to ensure proper feeding, functioning of the bolt stop and engagement of the magazine disconnect safety"
Those mark 3 mags I bought fairly cheap. You can order replacemant base plates for the mark 3 mags. I'm decided to modify the baseplate instead of replacing.
I have to modify MKII mags to fit in my old Ruger standard pistols.... ok, MKI pistols, but don’t tell anyone I called them that. Just a matter of reversing the thumb button follower assist and trimming the base plate. I’ve converted a dozen with zero issues.
I’ve seen the 22/45 mags go pretty cheap at gun mag warehouse btw.
You are correct. The mag bodies have not changed (to my knowledge) since the first series. Just the base plates, followers once, and the follower assist button. Glad to see another Ruger standard fan. I have almost enough myself.