They've changed their existing storage plans and policies. I bought additional storage for my photos through Picasa. The storage was made available across all Google products.

I had the 20gig for $5.00 plan. I say had, because I went to the Drive plan page and was told:

* Your current plan is no longer offered. Learn more.

The page redirect goes here:

http://support.google.com/drive/bin/answer.py?hl=en&answ...

No idea why it is called butter.

The excellent thing is that you are grandfathered in.