You are missing something for instance bump map.
http://webreference.com/3d/glossary/bump.html
Lets say to create a 2000 polygon sphere apply a bump map and you could make the sphere look like a dimpled golf ball that would nomally have 200,000 polygons. From the CPU end it is rendering a 2000 polygon sphere the graphics card does the rest of the work.
http://mirror.ati.com/vortal/r350/fl...nal/index.html
http://www.ati.com/vortal/r300/dx9demo/main.html