I won't say that I'm backing up this dealer, or that they're NOT suspicious, but I can certainly add some insight, and maybe some understanding.
I work at a dealership, and I'm in charge of our Ebay sales, even though I do not work in retail sales. We've been at it for a while as well, but we've also got minimal feedback. I'll let you in on the secret...
We by no means want the customer(s) to actually "purchase" through Ebay. We only want their attention, get them on the phone or in the store, and we want the sale completed solely through the store. And actually, with all emails that I receive through Ebay, we even try hard to NOT answer the questions, and only to get them to call the store, or give up their contact information. That in turn allows the window to contact away from Ebay. This does a few good things for us...
It allows us to charge the doc fees, title fees, and work with the financing which in turn makes the price flexible depending on the customer. Also, once we registered as a motor vehicle dealer, Ebay charges a fixed price for the listing, but we have to pay more if the sale is completed. Therefore, yes, feedback is good. But from the dealer standpoint, it's better for us to get the customer away from the site, and complete the sale directly through the store. It does create suspicions, but the determined customer matched with the right salesman will quickly drop their guard when we get in direct contact with them.
Hope I cleared that up!