My thought is that if you sand it, you are going to significantly alter the surface and the pan will never look "right" again. If you want it to be shiny, but keep the sand cast texture, you could use 0000 steel wool and WD-40. Or, you could use the tartaric acid method.
I probably wouldn't give $18 for it, but if you want an aluminum corn stick pan to use, I suppose that is a reasonable price. If it was for sale on eBay, it might never sell. There just isn't that much interest in Wagner aluminum Juniors.
I have a small blast cabinet with walnut shell media. It is a great way to save your fingers when cleaning waffle irons and gem pans.