Use Azure Table Storage Option instead of Azure SQL Database
Let's face it, compared to the Table Storage service, the SQL Database service is EXPENSIVE! Mobile app developers need the low cost option as well. This will surely impact query performance for complex queries but we're big boys and girls, we can weigh the pros and cons.
Serge van den Oever commented
With the current 20MB free SQL Server database you could do this without a problem. Just let your own API mathods talk to the Table Storage service, and don't use the table abstraction layer of Azure Mobile Services. Have a look at http://blogs.msdn.com/b/paolos/archive/2013/04/09/how-to-use-windows-azure-table-storage-in-windows-azure-mobile-services.aspx.