At the Jamf Nation User Conference, IBM shared their findings with deploying Macs vs. PCs:

In 2015, IBM let their employees decide – Windows or Mac. “The goal was to deliver a great employee choice program and strive to achieve the best Mac program,” Previn said. An emerging favorite meant the deployment of 30,000 Macs over the course of the year. But that number has grown. With more employees choosing Mac than ever before, the company now has 90,000 deployed (with only five admins supporting them), making it the largest Mac deployment on earth.

But isn’t it expensive, and doesn’t it overload IT? No. IBM found that not only do PCs drive twice the amount of support calls, they’re also three times more expensive. That’s right, depending on the model, IBM is saving anywhere from $273 – $543 per Mac compared to a PC, over a four-year lifespan. “And this reflects the best pricing we’ve ever gotten from Microsoft,” Previn said. Multiply that number by the 100,000+ Macs IBM expects to have deployed by the end of the year, and we’re talking some serious savings. [Emphasis mine]