Oh yeah...any true displacement adds to the poly count.  However, when working in Carrara, you can turn off the 3D view for displaced object (object is viewed – just doesn’t show displacement effect), so it won't add to the display burden.  However, it will show all displacement when rendering.  If you want to export a displaced object, you have to select “Displace in 3D view.”

It will be interesting to see how e-on implements its displacement mapping in Vue6.