You'd be crazy not to take tests to Melbourne, they're the most profitable destination for big, draw card matches (Bledisloe, lions and England, maybe Ireland and South Africa too). Crowd numbers absolute support those event games.
Taking smaller, non draw card teams there though? Feels like a bit of a non starter for the most part. Maybe if it was Fiji or Samoa and you're tapping into the Pacific market, but definitely not at premium prices. Better to take Wales to traditional strongholds and maybe a regional centre with a heartland rugby following.
Unless of course the state government is paying overs, but if that's the case you really want to get on top of the marketing.