I was a cop back in the era of Bill Ruger restricting the sale of his high-cap Mini-14 to "law enforcement only". Since that time, I've also bought quite a few of the newer factory mags which are now available to anyone who lives in a non-restricted state.
Just going from that....I'm perty-sure it's safe to say that yep, all of Ruger's Mini-14 mags have always been so marked.
As to what are used Mini-14 mags presently worth?......All I can say is that it depends. Over the past few months, I've seen used factory mags go for $30 or so each. On the other hand, I've seen vendors pricing them in the $20-$25 range lately.
Non-factory mags?.....now that's a different subject.
Aftermarket mags can be a hard sell, mostly because anyone who has been involved with the Mini platform over the years knows that most of them haven't even been worth taking home to fool around with, much less actually paying for.
There's one or two exceptions to that, sure. Back when they were still in business, PMI-branded mags were good, and there's a couple of more recent offerings which will usually run OK, or at least can be made to....so again, the answer to "what are they worth" is "it depends".
Details, that's what it all comes down to.
DGW