Yah the have different makes and models of those that all look the same. I am looking for the ones with the differential and double disc brakes.
You can find out lots of these trikes on google under Dune Cycle. I do not think they one in the link is a dune cycle. It looks like one of the nicer other brands they made. About 10 outfits were making these. Some were even street legal and front suspension and a tab larger.
The real value in these are if thery are all original. Looks like it only hit $285 on Ebay. This is not true value though. These also come with TC which this one does not have.
This one on ebay looks to be the same as the one in your link. If they are original like that then I can see $700 being a fair price. I thought it may have been restored and painted that color. I still do not think it is a dune cycle but I am no expert for sure. Heck they could be even be the same one not sure now.
http://cgi.ebay.com/ebaymotors/DUNE...rs_Powersports_Under_50cc&hash=item33772909f2