The latest update of Wunder allows car owners to decide the share of carpooling cost per Km they would want to propose to the passengers for the ride. However, the cost share shown to the passenger would only be calculated for the actual distance that the passenger would be carpooling with the car owner. This means that passengers could see different carpool cost share for different matches depending on the amount quoted by the specific car owner and the length of ride overlap between the passenger’s and car owner’s ride.
Note that the price is a suggestion. Don't hesitate to get in touch with the driver to negotiate if you feel the price is too high or too low!