If your average business is holding onto a Windows license for 3 years at an OEM rate that means that management would have to cut wages less than 1 cent per hour per employee (assuming each employee has their own PC) to make up for the costs of the Windows license. The cost of software license on the desktop are negligible compared to any productivity lost by switching OSs. Loss in productivity from using a new OS even without any training costs is going to cost more than to keep a known product on the desktop.