There is a built-in functionality for getting the costs:
The main problem with that functionality is that the smallest granularity you get is cluster/job because it relies on the cluster/job tags. And also there are problems with compute costs when nodes are obtained from the instance pools, as the nodes aren't re-tagged when used.
These problems could be solved by using the project Overwatch that allows to get more granular data, like costs per notebook/user/...
