Presumably it's AUD 1.00, not USD 1.00. The AUD is apparently around 73 cents US (I overcame my laziness to
check) so it's not 2x the rake you posit in US currency, only 1.5 times.
However, this statement seems theoretically flawed: "I can't see how it could be profitable to overcome a $1/hand charge in a limit game, no matter how fishy the game."
Suppose you get invited to a game where billionaire fish are playing $1000/2000 limit hold 'em extremely poorly for a time charge of $1 per hand. Bankroll/variance issues aside, that would be a +EV game, no?
Now, I don't know how AUD 5/10 plays versus say Foxwoods' USD 4/8 or 2/4 or whatever. Probably not fishy enough to make USD 0.73 per hand worth it. But in theory, the problem is the time charge relative to the stakes of the game -- not the time charge in absolute terms.