My guess he is good for about 350-450 k buys I would say, more if you give him a great match up or less if he has an opponent with less of a draw like say Werdum (dude is a PPV killer).
Now days close to a mill followers ain't exactly great levels I think Brendan Schaub is getting close to those numbers to put things into perspective. Noticed more activity on Instagram it's easier to have more followers there. Then again I'm no social media expert the only account I made was for Twitter way back and that's just so I can fallow some fighters/lesser stars that maybe benefited from more social media followers.
In HWs the draw king is Lesnar by far, then maybe prime JDS had a good fallowing that could do 500k buys then Cain, nowadays just the average 300k and Cain has inactivity issues so he will need a fight to reintroduce himself in the public casual eye.
The Champ Stipe went from 30k to 170k in 3 tittle defenses. Cleveland don't do twitter or what ? maybe MMA ain't that big even in his own city.