Well that's true. It helps to think of it that way.
Here is the thing. If you use copyright as a means to stop resellers from reselling your items then the resellers will just change the pictures and listings so that you don't recognize them as your yours anymore and continue to be resellers. Then you will have lost your only means of identifying who is reselling your products.
Instead maybe it would work better to raise the price on eBid once you see that your product is being sold by a reseller. The reseller likely won't know why you have raised the price and it will obviously discourage them from doing this. I think it was already mentioned but I like the idea of buying the item that is being resold if you are sure that it is really yours.
My point is that you're actually worse off if they buy it from you and resell it rather than listing it while it is still for sale by you.And as for more likely to get a sale for it here when its advertised elsewhere, that's rubbish