This may not be an exact answer to your question, but when I get our Azure invoice, the cost is always split into 2 parts:

1. the cost of the hardware/VMs etc. Basically the resources you use from the cloud provider. The cost of this is dependent on how much you use for how long (and what type of VM etc). This can be calculated using the cloud provider's cost calculator.
2. Then there is the cost of using the Databricks Service, which is expressed in DBUs. One DBU has a certain cost, and depending on what you do with Databricks, the amount of DBUs increases or decreases.

Calculating the cost is pretty hard tbh. F.e. using Photon is clearly more expensive than the classic engine BUT it can turn out to be cheaper because your workloads are finished way faster.