Azure billing data API
Azure now provides a way for customers to retrieve their usage and pricing details using the new Azure billing APIs: https://weblogs.asp.net/scottgu/new-azure-billing-apis-available
Windows Azure does not provide an API for billing/cost metering at the moment. Amazon provides CloudWatch for this.
Windows Azure Pack (for on-premises/SP cloud using Hyper-V) does have an API for cost metering.
The API is one of the most requested features by customers. See this link http://feedback.windowsazure.com/forums/170030-billing/suggestions/1143971-billing-usage-api#comments
I guess Microsoft is working on an API.So at the moment your only option is downloading the CSV. Microsoft recently added a feature which allows to receive email alerts when the monthly costs or total costs reach a customer set threshold.
The Azure Usage API can be called by customers and partners to get granular Azure resource usage data (hourly and daily buckets), and the response from this REST API is JSON.
Here are some more helpful links:
High-level article on Azure Billing APIs
Azure Usage API MSDN reference
Azure Billing API code samples on Github
If you have any other questions, please feel free to email me at mobandyo@microsoft.com.