Heya,
I see them in good shape for $200~250 new, right now, on ebay from a few sellers. The adapter is always $100~150 or so, as it's custom made. You could price it up a few bucks, for the simplicity of having them both together already, if you wanted to sell.
If you bought that lens for $100 and you put an adapter on it and sell it for over $300, you make a profit.
But frankly, I would not worry about "making" money here. You should just enjoy the lens. Or sell it and let someone else enjoy it. Also, frankly, I'm actually fairly put back seeing you say you don't want to sell something for what you paid for it, you want more. Really dude? I get capitalism and all, but come on. Knowing that I'd definitely not want to buy it from you. Just saying.
Very best,