This article says the Dockers are 6% up on memberships from last year and tracking for 43k. The Eagles are full up (50k) and have a waiting list for memberships of 9383 Families. :D
The only thing holding back massive attendance increases in Perth is the stadium size of 40k! This will be addressed when they finish their new stadium in the coming years.
Lets look at this further.

Meanwhile the broncos have 24k from 2 million people and the titans an Embarrasing 6k from 600k.
That's the difference boys. The AFL is so strong in its heartland it is now expanding aggressively. Meanwhile the NRL is struggling in its heartland and any thoughts of expansion are laughable.