If you're a New Relic customer, you can see your usage on our Usage Summary page. While the numbers are an approximation, you can use those views to get a general idea about how your consumption might affect your bill.
To view the usage UI, go to one.newrelic.com > (click your user name) > Administration > Usage Summary. This page shows an overview of your usage:
The New Relic usage UI
In addition to using the usage UI, you can also run queries to gauge your usage. For details, see Query and alert on usage data.