Google’s unified storage is finally here for almost everyone (it’s gradually being rolled out). The 25GB plan is no longer available and the entry level plan offers 100GB for $4.99/month.
You get 15GB of free storage for Gmail, Google Drive and Google+ Photos and you can buy additional storage (100GB, 200GB, 400GB, 1TB, 2TB, 4TB, 8TB, 16TB). Until now, the storage was only shared between Google Drive and Google+ Photos and you got 15GB of bonus storage for Gmail. Now the entire storage is shared between Gmail, Google Drive and Google+ Photos.