frustum culling problem

Hi!
I have a gameobject that has about 160 meshes as childs. It has baked lightmaps and no scripts attached to any of them.
There are no physics going on with these meshes.
The far clipping plane of my camera is set to 50.

Now i tried to instantiate that gameobject about 1000 units away and with everytime I instatiate it my framerate drops down by ~10%.
Same happens if i instatiate it visible to the camera.
Shouldnt the instances far away not affect the performance?

I tried it in the Editor, Webplayer and PC Standalone.
I want to use this to automatically extend the world when the player reaches the edge of the world.
(unity free)

Frustum culling isn’t free; Unity still has to go through all the objects every frame to figure out if they should be culled. So instances far away still affect performance.