Here you can find several cliff high quality models and example how to gather landscape using this models.

Triangles count:

Huge stone 1 - 6000 tris

Huge stone 2 - 4990 tris

Big stone - 5000 tris

Flat stone 1 - 2000 tris

Flat stone 2 - 5830 tris

Flat stone 3 - 3990 tris

Mid stone 1 - 4000 tris

Mid stone 2 - 960 tris

Small stones (for all 5 meshes) - 7018 tris