Samsung drops cost of KNOX to the low, low price of $0
Samsung can afford to price KNOX so cheaply because it isn't counting on its MDM business to make money. After all, Samsung is the largest smartphone manufacturer on the planet. Some of its MDM rivals also produce handsets, like BlackBerry. The latter's BES12 will be able to monitor a fleet full of BlackBerry, Android, iOS and Windows Phone handsets.
No question that Samsung has made things much tougher for its competition with the low pricing. Those using a KNOX enabled device can switch from using the handset in the traditional way, to having a container full of secure apps like a browser, calendar, contacts list and apps that are all designed for the enterprise. At the end of the business day, KNOX is turned off and the regular UI returns. The whole idea is to keep business apps separate from "playtime" apps allowing users to bring their own devices to work. It also prevents malware from infecting the enterprise side of the phone.
There is some speculation that Android L will contain some parts of KNOX so that all Android users can separate work data from play data.