You are right about the financial aspect. I'm sure that is one of the reasons why all the zoos outside China only ever have 1.1. pairs. It wouldn't apply to Australia but in areas with several zoos holding pairs, like Europe, if one zoo was to just house a couple of 'spare' males, instead of a pair, then they could move them temporarily to another zoo at that pair's mating time. They aren't difficult to move and the zoos always know well in advance pretty exactly the timing of oestrus periods for their individual females. Of course this is probably 'pie in the sky' thinking

and I doubt China would comply or be interested in more successful breeding in zoos abroad anyway, which might reduce their 'trade' value.
But I remember the ethologist George Schaller describing his observations of a 'mating gathering' in the wild- a quite complex process- and he later commented that the practise of zoo 'pairs' was detrimental to breeding chances. Of course there are exceptions and the occasional pair do prove compatable amd mate and reproduce naturally without stimulation from other males, but they are quite the rarity it seems.