They've had 2 sub 300k PPV's in the last year. 201 (Woodley vs Lawler) had 240k & 192 (Cormier vs Gustafsson) had 250k. There was a 3rd (195 Lawler vs Condit) that was right on the 300k mark so the actual numbers could have been less. The early estimates for 203 are between 650-800k.
If the predictions hold true for the 203 numbers, then I don't think you can deny Punk had a huge affect on that. Even Meltzer says he under estimated the wrestling crowd and that's his business. The problem for the UFC is that it's a one time bump and with Punk's performance, it won't happen again so how do they keep those numbers going? Outside of Rousey & McGregor, nobody is pulling in those kinds of numbers.