Very cheap, and do what they should. I've had a paper pair for ages now, and after moving house they ended up creased and wouldn't sit right. These plastic ones are perfect - they fit right (even on my big head) and the lenses are bigger than on the old paper ones, so provide a more immersive experience.
I use them with an Nvidia graphics card with 3D stereoscopic enabled for games, at the default levels, and find it perfect. If you increase the 3D depth the image does start to separate, but that may be something that improves as you get used to it.
All in all an excellent purchase for those who can't afford a 120Hz monitor and full 3D vision kit.