The other factor to consider is whilst other clubs marketing budget is spent (predominantly) locally, ours is not - so we may well be spending comparable $$$$ overall but that budget is layered more thinly due to the breadth of our "home" games.
What Welnix must do (as well as the onfield stuff) is be smart with their promos, and probably a little leftfield (pun intended). The bus/shelter thing has become a little anonymous now and whilst I'm sure it's great "value", I would be surprised if their weren't other avenues that would provide a better ROI - in particular consideration of the niches in which we can, and should be, targeting.
We have a stable base (us, and the others who make up the 5k or so people that turn up rain/hail/shine/fri/sat/sun/5pn/7pm/3pm/whatever) but the club NEEDS to directly engage the other 5k who would probably come come if we were winning, and the additional 5k that will come when the Nix are the "hot" thing in town... all of this becomes a lot easier; and cheaper - when the team is winning regularly (regardless of the style of football).
As part of the new license the FFA has agreed to increase the advertising for the A-League as a whole in NZ, one of the problems is that people watch the Phoenix but they don't have second teams in Australia to support and watch. Sky is only going to up what they pay if ratings for the A-League as a whole improve, not just the Phoenix.