It's not about the teams, it's about the thousands of members who pay potentially a grand or more just to get to the first grand final, even from Sydney let alone Perth or Queensland.I was at the 2010 grand final and the replay. No doubt in my mind extra time is the right option for the players on the day, fans and the league.
That said, why couldn't interstate teams stay the entire week in Melbourne? They could easily book hotel rooms for a week and train at any one of the at least 9 Victorian clubs training bases. It's unlikely Melbourne will be in a grand final any time soon, so presuming Victory and/or Storm aren't busy they can use the shared AAMI Park facilities without accessing any intellectual property. It's kind of a moot point but I don't see why teams from QLD or WA would even fly home.