Oh God this topic is funny.

To be a bit serious I once made a floor that had 1024 pyramid meshes on it laid out in an even grid. When they were all in view it ran like crap on a decent computer. When only a few were in view it was fine. When I put them all in one mesh and had only 1 entity and not 1024 it ran just fine. As you see there is more to this then just poly-count.