One of the links that was posted above still has some time left on eBay. The price isn't too bad right now and shipping isn't too bad as well. Here it is again.
http://cgi.ebay.com/BRINLY-DEERE-CASE-C ... 27b967328a
I use the Brinly one bottom plow (moldboard as some would call it). I picked mine up from Craigslist. (I actually have two, but Jack has been promised one of them.) As well, I have a 3-point older Sears model that I am going to be selling here as the weather warms up. So, to ultimately answer your question, you are going to pay $100 to $150 and I would ask around and watch CL and eBay.
For those whom have not used one, they are one of the best tools I have. They break new ground well and after the garden season it works well getting all of the vines out and turning the dirt. My tiller gets jammed up with the vines and it will not break new ground like a plow. The tiller is good to smooth out the bumps and clumps. Just my thoughts...
-Justin