Hard to say, others will chime in. I would say, despite it being NOS, that it is still a core. I would go through it before using it. Old gaskets would be dry, insects could have crawled in, died or packed in mud, blocking jets, idle passages, etc. How's the finish? Any rust?
If the base/linkages are rusty and the die cast body corroded or pitted due to moisture/weather exposure, it would be a $50-$125 core. To me, if it looks like a typical used core, then that's what its value would be.