I bought a used vehicle last month from a dealer. I paid GST+PST+$100 for plates. Since my birthday was only a few months away, the dealer only needed $50 for plates+sticker and put in $50 worth of gas. He gave me the receipts from the MTO and Sunoco when I came to pick up.
I know a lot of used car dealers will say their "fees" are not negotiable. I suggest not arguing over the line items. Figure out what you would like to pay out the door and make them a final out the door offer. I'm guessing you don't need this vehicle right away, it is not a hot mover and it is a "summer car." Worse case scenario is you will have to wait till January before acquiring that vehicle at considerably less than today's price.