Ask HN: Has anyone migrated a Mongo db to Azure Cosmos witho draining credit?

I created Azure CosmosDB instance for MongoDB APIs and migrated my existing database to Cosmos. There was a restriction on unique indexes that: Unique indexes can only be created when collection is empty. So I emptied collection by "removing documents". But index won't appear. I dropped collection and created indexes and restored the collection from backup. Plus, during testing this out, I created and dropped individual collections & whole database 4-5 times in duration of 24 hours. I woke up to see that the cost incurred on Cosmos was $144 for requests made during last day. Database size is hardly 300KB when compressed (so around a couple MBs).

I still have not been able to get my head around RUs (Request Units). Docs say: A request unit is a normalized measure of request processing cost. But IMHO, RUs are much expensive [1]. What was your experience migrating/maintaining Mongo to Cosmos?

[1] https://docs.microsoft.com/en-us/azure/cosmos-db/request-units#estimating-throughput-needs