I would expect him to cut at least $10 off the price, based on his mistake. The fact that he specifically says the shifters aren't included legally infers that everything else is included.
If he won't give you some compensation for his mistake, institute a grievance. I suspect the seller is just disappointed that the bidding didn't go higher.
I had the same thing happen to me when I was buying a Wii for my son. The seller was disappointed that the bidding didn't go higher and alleged it was a mistake that she advertised that it included 3 games. I raised enough hell that she refunded me $100.
One of her arguments was that I should have known a Wii with 3 games was worth a lot more than $350. At the time, that bundle was going for over $500. Fortunately, the Ebay rules don't allow the sellers to determine what they are selling, after they have been paid.