Those look like the Norinco 84S mags but the rifle is a Polytech AKS in .223 which had a different style magazine, originally. I've read that the mags are not interchangeable but don't know for sure.
As you were told, and can see on the rifle, it is a Poly Tech AKS-223 that came with Norinco 84S mags. As you also found out there is a way to modify the 84S mags to work in the Poly Tech. I don't believe that Poly Tech mags can be modified to work in the 84S but you wouldn't want to as they are so expensive. I also have 84S mags modified to fit both but unfortunately I can't remember for sure what the mod is but I believe it has to do with the locking lug.
As to value, the while the .223/5.56x45 version of the AKM is not the most sought after, those with the underfolding bayonets are still very desirable and can sell for around $2000 if not more.
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