BYOD isn’t about cost reduction; it’s about responding to psychologically driven demands from end-users. Employees in today’s consumer-oriented culture expect to be able to “have it your way,” regardless of whether there is any financial benefit to the business.
Back in the 20th century, Big was a good thing. Economies of scale meant that Big could produce things faster and cheaper. Big used to mean stable, reliable, bulletproof, Indestructible. This is no longer the case.