Why is this simple low poly asset destroying my framerate?

Hey!

One of my game assets, a really simple nail, is eating up my framerate. The game runs in the editor at around 90 FPS, but when I add six of the nail models, it drops to around 5 FPS.

There are no scripts, colliders, or effects applied to the nails. The framerate rises back to 90 FPS when I turn off the nails' mesh renderer, but the mesh is extremely low poly and shouldn't have that much effect on the framerate.

I tried deleting the nails and adding the equivalent number of polygons with other models and the framerate remained in the 90's.

Does anyone know what might be causing this? Thanks!

http://answers.unity3d.com/storage/temp/30002-nails.png