Sorry but how exactly does Sydney airport charge for terminal transfer?
I suspect probably no inter-terminal transfer in the world is free - somewhere, in your airfare for example, or in a separate cash transaction paid direct to the transfer operator, or in some other way, you're paying for it.
However if I turn up to an airport, and need to migrate from one terminal to another (and it is not walkable), I do not expect to have to fork out a separate fee for it, just as if I use a travelator (moving walkway) to get to some far-flung gates in the same terminal I don't expect to pay separately for that. Same goes for travel from the long-term airport carpark. I am in the one airport and I expect (quite reasonably, I think
) not to have to make a separate payment for travel within that airport - how that is structured 'behind the scenes' is not my concern (I'm quite sure SYD gets at least some of it).
DFW, SIN, LHR and AKL are all examples of airports where there is no 'extra' or separate charge to commute between terminals, and this is what I would expect at SYD, and as a transferring pax, the underlying 'who is paying who' should not enter into it. IMHO.
So to answer your question (or actually, to
not answer it as I do not know the answer
), looking from another angle, I expect SYD to provide inter-terminal transfers for me where I do not pay a separate fee - how they manage that is up to them.