off the top of my head, I'd say a shitload of money.
think mid $XX,xxx for them, perhaps as a set. Give it 3-4 years and ethanol will be roughly 25% of the Domestic (USA) automarket if nothing changes on the gasoline price front.
If prices drop soon, extend that to 5-7 years. I would hold onto these, but if pressed for cash... contact exxon/mobil or that british owned one.. name eludes me at the moment.