Why are some tournaments succesful?

Actually I have no idea. It is actually a source of frustration with me that a well organised tournament with good prizes and conditions struggles to attract a reasonable size field, while an event that doesn't do anything special gets flooded with entries.
An example is three tournaments being held this long weekend. There is a tournament in Sydney ($75 entry fee), one in Melbourne ($55 entry fee) and one in Brisbane ($40 entry fee). Now I haven't seen the standings from the Sydney event, but based on the list of top seeds (Antic, Bjelobrk etc) and the fact that some Canberran's were making the trip to play, I'm assuming that it will be a well attended event. On the other hand the Melbourne event had a field of 22, and the Brisbane event a field of 20.
Now I don't think the difference is the "chess culture" in each city (as each has held far more successful events both recently and regularly), or even the publicity is to blame (as I have seen all three advertised on the net, and both Melbourne and Brisbane seemed to "push" their events more).
This leaves me to think that this may be an example of "targeted networks" being encouraged to play. By "targeted networks" I mean players who have a social network, and will often play as a group. This could be members of the same club who feel like some weekend chess together, chess players who also hang out together off the board, or even sets of people who use the tournaments to meet up.
The advantage in identifying these groups is you don't just get 1 player per advertising "hit" but 4 or 5. A further refinement to this strategy is to locate "opinion leaders" and get them interested in the event. This will then get their direct group to play, and even sweep up indirect contacts as well.
Of course the challenge is to either find these groups or leaders, or even to create them. How to do that is of course the big question. And one that I'll keep thinking about for now.