Cheapest Mac WebcamsThe best dirt cheap Apple compatible web camera comes from premiere brand Logitech. It has good software support making it a no-brainer for the flexibility of an easy to position external Mac HD webcam with built-in mic. You wanted the cheapest - but from the best name in the webcam business - this is it. Do note it's fixed focus and lacks a tripod mounting hole, so it's rather no-frills cheapness best for video chat. Those into capture or streaming ought to look for cheap 1080p web cameras for higher frame-rates and a more detailed image.
Great Apple Compatible Webcam Settings and Capture Software