Scandoublers aren't difficult to find. Scandoublers in their usual sense, maybe, but there are many alternatives.
Yes, the card sold at 179 USD, but that's new, and not a used one. You have to take that into consideration. If you base your price on ebay sale prices, you will have to relist items over and over again. Anyway, you are looking for maximum profit, so all you can do is to wait for the right one to come along.
As for the scandoubler, yes, it's a good scandoubler, but there are others in equal quality. There are others I'd go for first.
Anyway, good luck on your ebay sales, I'm sure this isn't the last one of your FS threads.