Azure Cosmos DB offers a free tier for new accounts i.e. 400 RU/s (Request Units per second) and 5 GB storage per month. Azure Cosmos DB charges an hourly rate for the provisioned throughput and consumed storage. Provisioned throughput bills $0.008/hr for 100 RU/s single-region account. Also, $0.016/hour for 100 RU/s multi-region and multi-master account for a region.
For consumed storage, Cosmos DB charges $0.25/month for 1GB of consumed transactional storage. Cosmos DB charges $0.02/moth for 1 GB of consumed analytical storage.
If you want to learn Azure Cosmos DB, I suggest you enroll this Azure Data Factory training by Intellipaat.
You can watch this video on Azure Cosmos DB tutorial to know about Azure Cosmos DB pricing: