Most auto parts stores carry them, or can get them. Also, try truck stops. They frequently carry them as well. And, since they are apparently for your Ventana, there's always the "mother ship" parts store in Nappanee. I'm betting your local auto parts story will have them, however.
Pricing at the Service Center parts counter is a fascinating subject. It may well have something to do with the turnover of the item. If a part is a slow mover but necessary to stock, that part is much more expensive to stock. A part that turns over at a fast pace is profitable at a much lower price point.