Enable to view on dashboards the PAAS file-storage usage. Per day, so to monitor both current status, and the growth (costs) indication.
In PAAS, enable showing on dashboard how much of my 'file storage' is in use, per day. Either as a FILESERVICE Capacity 'metric'. Or as a FILESERVICE 'Usage' indicator (alike already does exist for BLOB SERVICE).
So I can see wether my file usage is 'stable' (as should), or slowing growing over time, and thus growing in costs (as should not).