Looking for application which will provide to determine project database growth and cost per day or month

Question

I am using SQL Server 2008 for product development

Currently application is live with 20 users now if I want to check how my database is growing and how much it will grow in month or year projection to determine the cost of hardware. Is there any application or SQL Server built-in function?

Using SQL Server profiler I am able to monitor database queries and fine tuning.