According to this Tech Target article by Beth Pariseau, “Cloud computing costs can soar when new customers assume that an initial deployment needs to be as large as the internal infrastructure being converted to cloud.” This came from several interviews she did with IT leaders who are surprised at how much cloud computing costs.
Overall, many overbuy cloud-based services in an attempt to replicate their current on-premise systems. Typically this is not the right approach to cloud computing, and will lead to some larger invoices that many who move to cloud computing did not expect.
Key to the issue is that “Server instance redundancy for disaster recovery is an often-overlooked cost, according to a director of engineering for a Fortune 100 company who requested anonymity. Any new cloud deployment for this company requires at least 12 to 24 machines, just to have a presence with the proper redundancy and controls in place.”
The key to avoiding these surprises is planning. Cost planning needs to come along with the technology planning, including the ability to add costs for redundancy, data retention, service demand during peak loads, security, governance, etc.. These need to be considered, and included in the analysis. Otherwise, prepare to get some bills from your cloud provider that will kill your budget.