The cost of a Cloud DMS is influenced by a variety of complex features and performance, and needs to be scanned closely before-hand. Storage with low latency tends to cost more than one with high latency. Secondly, while archival storage comes at an affordable price-point, functions such as interactive and batch processing tend to command a mark-up. Data egress, copying data between data centres, frequent large transfers and automatic versioning will also attract a higher cost. Cost will perhaps not be a big deterrent when it comes to switching to the Cloud, not least because of the substantial savings it will deliver in the long run. You must nevertheless factor-in the full lifecycle of data to calculate the approximate costs, before taking that final decision.