Ok.
So let's ignore the Giants. Why?
Because in 2015 they averaged 10k attendance which is less than the force and were founded on huge capital injection by the AFL and huge draft concessions.
Most proponents of the force argue if the ARU had been able to provide that type of support they'd be in a much better position.
The Wanderers average 12k at every home game. Basically the same as the Force, but were initially very successful. In their first season Sydney FC had their average attendance spike at 18k but it has since dropped slightly each year down to the low 17ks basically on par with their first ever season.
So the Giants pull less fans, the Wanderers only pull the same amount despite quite a bit of initial success and over time after an initial spike, Sydney FC have dropped to their first year levels.
The swans saw their average attendance drop by 5k the year before the Giants entered the comp. This was despite their climb from 12th in 2009 to finish 5th and 6th in the next 2 seasons. In the Giants first year they finished 1st, won the Grand Final and were still down on average attendance prior to GWS.
Their average attendance in 2015 was 700 higher than 2010.
So the swans have definitely seen an impact.
Then there's the other considerations.
If there was a Western Sydney team, would they play at Homebush? If so would the stadium have offered the same incentives for Waratahs games. The team made $400k in 2014. Take out the crowds from 2 Homebush semis and incentives for their Brumbies and Crusaders games and it's probably closer to a $400k loss.
The Giants are a long term investment by the AFL.
Even on your figures (which I accept in good faith) GWS get 10,000 per game - so even if it's correct that Swans dropped 5,000, that's still 5,000 more going to the game. But it's bigger that the short term crowd figures - in the lead up to the Sydney derby, there's a marked increase in AFL coverage in the papers and on TV. Additionally, the AFL now has two vehicles to promote grass roots participation. Also more opportunity for sponsor involvement in the sport.
Similar story with soccer - a small decrease in Sydney FC fans, but 12,000 fans going to WSW games - so a net increase in crowds of over 10,000. Same media story in derby weeks - soccer coverage in Sydney goes from part of a page 3 pages from the back to 3 or 4 pages. Like the AFL, it's good news for soccer.
If there was a 2nd super team based in Sydney (which won't happen by the way), one would assume it would be based at either Parramatta Stadium, Penrith Park or the Sports Complex at Blacktown (unless Homebush gave them an offer they couldn't refuse). I suspect that this imaginary team would make little impact on the Waratahs, but any impact would be offset by fans going who don't/wouldn't go to watch the Waratahs (i.e. new fans). Should this imaginary team ever get past the musings of us on the internet - it would have 2 significant impacts:
1 it would provide a second vehicle to promote grass roots rugby
2 it would serve to address a serious shortcoming inherent in super rugby - the lack of coverage when the Waratahs are away (particular in South Africa)
Please note that in the current climate I am not advocating the establishment of a second super team in Sydney.
I'm not sure what targets that the ARU have set for the Rebels and the Force in terms of grass roots development. If the desire to to have two professional sides operating out of Perth and Melbourne without builidng a solid junior and grass roots programme, then both are doomed to be permanent and expensive money pits.
All of the above illustrates the enormity of the task ahead for rugby in Australia. Rugby doesn't have the money to do everything which needs to be done, let alone should be done. And I remain convinced that those charged with running the game have no idea of the extent of the problems facing the game, let alone how to go about solving them
