CPU cost of using multiple rigidbodies

What is the CPU cost for using kinematic rigid bodies on an object? I'm trying to design my game for mobile, and I'm not sure how much CPU cost there is in using kinematic rigidbodies. For instance, let's say my taxi prefab has two children to it with these components added

 1) Taxi (Gameobject) //used for detecting vehicle triggers, so if too close behind a car we can register it to slow down
    --Box Collider (trigger)
    --Kinematic Rigidbody
        1a) Vehicle Trigger //follows behind vehicle as a collision zone for others
             --Box Collider (trigger)
             --Kinematic Rigidbody
        1b) Mesh (Gameobject)  //used for player/vehicle collision
             --Box Collider (solid)
             --Kinematic Rigidbody

As this could be resource intensive with the collisions, I already have everything split into different layers to minimize waste. I also plan on paging vehicles (disabling vehicles that are out of range of the player), but I'm just wondering how much processing power each rigidbody takes up.