The Seven-Digit Savings

On the cost side, VMware put a cap on the amount of reimbursement per employee so that wireless bills wouldn't spiral out of control. The amount varied depending on job function: a quota-carrying salesperson was allotted up to $250 per month, while most employees capped out at $70.

"I know what my phone bills were, and we're about 30 percent lower" with BYOD, Egan says.

BYOD cost savings, however, don't come easy. In fact, Aberdeen Group found that a company with 1,000 mobile devices can spend an extra $170,000 per year, on average, when they use a BYOD approach. (For more on this, read BYOD: If You Think You're Saving Money, Think Again.)

The problem lies in hidden costs: BYOD often leads to more expense reports filed every month, and a single expense report costs about $18 to process, Aberdeen says. This pushes up the average cost of a monthly BYOD phone bill to $90.