Ebay has very strict rules about abiding by its very strict rules. The seller is breaking a legal and binding contract by asking you for more money. If he continues to do so, you have the right to sue him. Email or call ebay and inform them of the situation. Either they will take care of it or they will tell you what steps to take. The seller is legally bound by law, not just ebay law, to sell you those rims for the auction-win price, just as you are bound by law to buy them. An auction is a legal contract.

You are in the right. You did have three days to contact seller, and even longer to submit payment depending on terms of sale. Take action immediately to ensure your rights and standing as auction winner.

Please keep us informed.