Osage probably bought the last of them...maybe thousands? And they trickle them out a little at a time. Same thing happened with CZ 452 rifles. Out of production for many years, yet one or two sites(really, mainly one was doing it) have 20-40 available every 10 months or so.When I called Sig, they put some mags on back order.
When I emailed them the guy claimed Sig no longer made them. I have a hard time believing that as OGC got a pile of them in.