If I didn't have my antique shellers, I'd sure consider this one. I don't know how long the plastic sheller wheel would last, but it could be pretty good. Wait until the corn is very dry and it will usually shell easier anyway.
I too rebelled at the cost of the new cast iron ones, like the one sold by Lehman's store. That one, FWIW, I am pretty sure is made by C. S. Bell Co., in Ohio. I have one of their burr mills I bought 35 years ago and still going strong. Good stuff, and they STILL have parts for it! I recently bought a new set of cast iron burrs "just in case" then found that the originals had no measurable wear on them after grinding feed for livestock for years.
http://www.csbellco.com/grist-mill-60.asp Mine is the larger mill, bought without the motor. It will do about 200 pounds of chicken feed an hour, and flour at 40 to 50 pounds/hour, since I run it through 3 or 4 times. I have a 1 1/2 HP electric motor on it, which is about the minimum. 2 HP would be better if you are going to push it grinding animal feed, but it is a workhorse as-is.
I would buy Bell's corn sheller in a heartbeat, but it is going to cost far more than the one you found.
I'd try the popcorn in it anyway. If it only gets half of the grains, so be it. It would be a lot easier to do by hand once half of it is shelled!