The number of games out of Melbourne is a sacrifice, but it's for the good of the game (live football in places that wouldn't get games otherwise)...It also has the practical reason of the stadia in Melbourne not being able to handle more games.
As for SA/WA...There is a big difference between games being sold to venues that wouldn't get games otherwise and to other teams home venues. A game in Broome (for example) would be a different matter to a game in Perth.
Another example of AFL equality, non Vic clubs travel 10 times each year, surely Vic clubs could travel a minimum of say 8.
Its not as if playing at home is sacred for many clubs, its just about money ... & there is supply & demand.
WAFL clubs regularly play in their zones.