See running costs in portal / cost management
The page https://account.azure.com/Subscriptions lists subscriptions and for each subscription, I can see the current usage of that subscription. Azure offsers Cost Management (Cloudyn) -- I suppose they offer better insight and more elaborate analyses -- but the data included in the linked account page could be very useful.
It could very well be that it is already included somewhere, but I can't find it?
This is already available for Enterprise Agreement (EA) accounts today and will be available for pay-as-you-go and dev/test subscriptions soon. CSP support is also planned and will be available later.