"Real Memory" usage in iOS expands the more often one prefab is referenced in the assetbundle

Hi everybody, We have a car racing game and there is only one scene from which we load different racing tracks using assetbundles. Inside this assetbundle there are many cars, all referencing one prefab. In Unity Editor in the profiler it makes no difference regarding Real Memory if there is only one car or 10 cars in the assetbundle but in iOS it takes much more Memory if there are 10 cars instead of only one car. (profiled by the "Activity Monitor" in Xcode) Anyone got an idea how this can be? Unity Editor doesn`t change Memory usage according to the number of cars. Thanks in advance