i think you should do it $1 at a time. from $15 to $25 is a big jump. try first $16. if you still have full capacity, then you can add $1 more. once you get non-full capacity, then just deduct $1. that's your ideal ticket price for that level.
topeleven is not so logical regarding this. you have more than 1m fans, yet can't fill less than 100k seat. 11: 1, you should get full capacity at top price.