License plate cost (sticker) for pickup in Ontario...

See here.

Should be $120/yr in southern Ontario, $60yr northern. That's what it lists for passenger vehicles as well as commercial vehicles for personal use. Your truck because of its GVWR may be automatically considered a commercial vehicle.

The weight of your fiver or anything else in the truck has nothing to do with it. It's all based on the registered empty weight on the ownership.