Funny you bring this up. I couldn't pull the trigger on buying an SG last night 'cause of the price. I know myself, it would get used so whatever value it may have as a new mag for collecting, it would lose. Already accidently took the Rockola Clark to the range - and that had been NIW when I bought it. Was planning to save that for someone with a Rockola that might want to buy or trade. I have several S'G' but thought it would be nice to have 3 total that would have been the type delivered with the carbine.
On the other hand, last year I wanted another mag for a modern pistol. I bought it at my local range/gun shop. Ouch! IIRC it was about $40 with taxes. Doesn't hold 15 rounds either. LOL.