A salary cap is a blunt tool though. I've no problem with Man Utd spending lots of money because they have earnt it themselves through a very slick commercial organisation. It's less palatable when a sugar daddy comes along ala Abramovich and raises a clubs spending far in excess of its operational income but would we feel the same if we had such a benefactor ourselves?
In rugby the turnover of champions generally happens because of the turnover in players. So a club wins the league, its players then generally want paying more (as champs), the club can then no longer afford to keep its squad together so have to offload players and rebuild. If we somehow got to a position of being champions and then were forced to offload a Cahill or Arteta, not because they want to go, not because we don't have the cash to afford them, but because the rules dictate we have to, I can't see many fans being happy with that.
In rugby the turnover of champions generally happens because of the turnover in players. So a club wins the league, its players then generally want paying more (as champs), the club can then no longer afford to keep its squad together so have to offload players and rebuild. If we somehow got to a position of being champions and then were forced to offload a Cahill or Arteta, not because they want to go, not because we don't have the cash to afford them, but because the rules dictate we have to, I can't see many fans being happy with that.