Honestly, a wing by itself is worth almost nothing (around here anyway). I see the same ones come and go on Craigslist for months at a time for about $100.
But, if the wing stands / supports are in good shape - meaning no cracks or stripped mounting holes, then it has some value. Whenever I find a wing in the junk yard I just grab the stands (if they are in good shape) and leave the wing. I have seen a set of stands sell for $75 to over $150.
If the threaded insert in the wing is bad or missing, it is just a well nut. They're generally available at larger hardware stores or Fastenal. Anytime I have the stand off an original wing, I replace the well nuts, any way.