With CirrusGrid you only pay for consumed resources. The prices can be seen inside your CirrusGrid dashboard.
Navigate to Balance > Quotas & Pricing menu item. Here you’ll see a set of tabs displaying pricing information for each kind of resource available in CirrusGrid.

Choose the one you are interested in to see the pricing and discount scale. You can find more information about pricing and discount systems in the Pricing System and Automatic Discounts documents.
Note that the various software stacks are provided free of charge in CirrusGrid. You only pay for the resources consumed but not for the software itself.