I am not a licensed attorney in the state of Nebraska, but I am in Texas. The Uniform Commercial Code has been adopted by every state in the United States (but for Louisiana), and this is simply a breach of contract, as most of you guys have noticed. An eBay contract is a legally enforceable contract, and the dealership should have delegated the authority and responsibility to list the M3 to an employee with knowledge and experience setting the terms. Salespeople, even those who do it online, have the vested authority to make sales, and thus the company that owns the dealership will be held responsible for the acts of their agents.
I wish I was in Nebraska. I would do it just for fun. I might even throw in a Deceptive Trade Practice claim, on which there would be treble damages and attorney's fees awarded. Throw in the words "Deceptive Trade" in your next conversation. Nebraska has a Uniform Deceptive Trade Practices Act.
87-302. (a) A person engages in a deceptive trade practice when, in the course of his or her business, vocation, or occupation, he or she:
(9) Advertises goods or services with intent not to sell them as advertised;
With regard to the BBB, they are really just an Alternative Dispute Resolution mechanism. They'll mediate your dispute, but it's not necessarily binding on the dealership. The dealership will only jeopardize their membership with the BBB if it turns in your favor and they do not honor the resolution (I do not know how much that means to them). I would recommend, if you have a mediation, that you go in fully prepared.