since you are asking for constructive critiscism....here is my 2 cents....
Captain Tomaday US - a little high on the "high" price, I'd top out at $85
Magician Lord US - a little low overall I personally, based on times seen here and on ebay, I would put it at $30-$50
Metal Slug 2 US - a little too high on the "high" end. ebay is flooded by sellers where it can be had original with label/serials intact for $29.99
Prehistoric Isle 2 US - this is where I would have to disagree the most on the "low" end. I would have LOVED to find one for $60...for the 3 months I looked nonstop, I came across 4 copies, be it here or on ebay...they were $118.50, $139, $144, and I finally settled on buying one from a wonderful seller here for $125. That was looking at yahoo and ebay auctions every day for 3 months. I would say the absolutele low at $100.
Sengoku 3 US - I would say again low overall...I would put it in the $70-$90 range....anytime it pops up here there are tons of people willing to bite down at around $80ish.
Windjammers US - low overall...it just doesnt pop up that often to warrant the price be that low...I have NEVER seen it for less then $35, but have seen it go as high as $55-60 on multiple occasions.
well thats pretty much my 2 cents on the ones that I am knoweldgeable on.....I don't know enough about the frequency of availability on some others so I shall leave the comments to the vets on here....again, thats my 2 cents......thanks again for making the list current !