Migrating from on-premises to the cloud is often fraught with unexpected problems, which can easily lead to unexpected expenses as well. What appears to be a simple act of lifting and shifting servers and data into virtual infrastructures becomes bogged down in a morass of issues—followed by demands to repatriate services back to your data center.
Chalk it up to a fundamental disconnect between on-premises architectures and cloud architectures. On-premises systems are all about getting the most out of hardware, often running a single service on a single server. The cloud is very different, and performance is less of an issue. Instead, cloud providers like Azure aim to take advantage of economies of scale, running multi-tenant hosts that use hyperscaling techniques to ensure that servers run at close to capacity at all times.