There are additional costs associated with storing HIPAA data in Azure; primarily due to additional logging. If you are interested in a HIPAA-approved subscription in UIC's Microsoft Azure environment you should be aware that there are extra security and compliance controls applied to HIPAA subscriptions. A sample list of the controls can be found at Control mapping of the HIPAA HITRUST blueprint sample.
For a single VM, Technology Solutions estimates an additional cost of around $9 a month in log retention (per VM). This is only an estimate. Microsoft estimates that an average Azure VM creates 1-3 GB of logs a month.