As I started with 3D on a computer with 1MB RAM I'm still counting polys, always trying to make as few as possible
The number of polys you use depends on how many details you want, and how many pixels you have available. For a 500k model I guess I would have had to shoot some closeups too. Or just PhotoScan the main shapes and use other tools for details. It is perfectly possible to make a detailed model in PhotoScan without using the Surface/Image matching tools. There are very powerful upsample/downsample tools, as well as smooth and redistribute functions. Vertex locking and fixing are extremely useful for many tasks other than modeling from photos.
One of the great things with PhotoScan vs ImageModeler and Photomodeler is that you can use all the powerful tools and plugins in SU. The sides were here made with TIGs ExtrudeEdgesAlongVector.