It will take deliberate disconnection of files from a vector store by API command or deletion of the vector store to stop the billing for data placed in them, due to vectors and text extracted from files remaining after files are deleted from storage.
Uploaded and created files in storage are at no cost, up to 1TB max. Batch job data expires after 30 days.
Fine tuning is essentially an unlimited model count, after your up-front costs, with any training file uploads or output reports remaining until deleted.