Quantum Key Distribution or QKD offers a quantum safe mechanism to establish an encrypted and authenticated communications channel. QKD is theoretically secure against a computationally unbounded adversary; this contrasts with classical key distribution systems where security is contingent on the assumptions made about the computational capacity of the adversary. These systems are being deployed in operational test environments across the globe. Most commercial systems require expensive proprietary technology, where the marginal cost of deployment is proportional to the capital investment. This means that the cost of adding an additional user is proportional to the cost of the original system. Thus, some experts have argued that the security assurance of QKD systems is not adequate to justify a transition from current approaches, other than for niche or otherwise narrow use cases. This paper provides an overview of current QKD systems, provides insight into the economics of deployment, and discusses the potential for commercial applications.