Well my arena will be small, probably about 5300-5400 or so. My prices right now are all fairly close to the point at which attendance is maximized. Would about 30% still apply? Looking around at D.IV leagues, it seems that would put me about on par attendance wise for 1- and 2- seed teams with similarly sized arenas.
I was asking a similar question recently, regarding my own potential promotion.
I won Div V outright, but then I bot promoted from Div IV to III, so I didn't see the attendance boost.
Thus, I was curious about how to set my prices if and when I promote to DII.
Anyhow, I can't find the response I got, but it was along these lines.
Find the top team in the league you are promoting to, and model your prices after them (modifying for number of seats), and then tack on an extra 10-15% in prices. All other things equal, your attendance should perform better than the top team in that league by about 10-15% until your promotion bonus ends.