Price On A Factory 318 Poly 4bbl. Intake Manifold?

Can any of you guys that are in the know, tell me what a factory, cast iron, 4bbl. intake manifold for a Carter AFB, are selling for in this modern day and age?
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How much is it worth to you? If you're building something with a poly and need it, it may be worth more than if you're just trying to buy it for cheap to flip for a few bucks.