The cost depends on whether it's electrochromic or not. Just the plain heated ones aren't too bad, but having the auto-dimming function basically triples the price. And since the connectors for the two types of different, installing the non-electrochromic one onto a mirror that had the feature means that although the functionality and adjustments work fine, you lose both the heat and electrochromic functions. So ultimately it depends on what options your vehicle has.