Opensolr now provides a very nice way for users to manage their expenses, via our Post Paid Billing System.
Long story short, if you are at all familiar with the AWS Cloud, or the Ali-Baba Cloud, our system will work pretty much in the exact same manner.
The stats in the image below can be found in your opensolr control panel, under Billing->Post Paid Balance & Status

Please submit a request to support@opensolr.com in order to become a post-paid billing member.

Here's a demo screenshot that lists our post-paid pricing table, and the post-paid billing control panel.