Where to find current "Per Tb Per Month" mining reward number?

Based on last 30 days of mining data. Assuming it's easy/available, would be great in comparing to other hdd uses.
The closest napkin calc I could get to was around $1.29 but it's changing all the time right?
Any help appreciated!
Thanks.

http://burstcoin.biz/calculator Is this what you are looking for?