Additional expenses are involved if a team plays most of their matches in neutral venues. In case of UAE, the taxes are not there so the expenses may be low, but even then it will turn out to be a loss making proposition for the hosts. So I understand the reluctance from the part of the South Africans. But the Australians are perfectly justified in their stance. Right now it is not safe to tour South Africa. Yesterday they had almost 4,000 new cases and around 300 deaths from COVID 19. The situation is really bad there and if the Australian players think that the country is not safe to tour, then I can't blame them.
BTW, there is good news from Pakistan:
https://sports.ndtv.com/cricket/psl-2021-fans-up-to-20-stadium-capacity-allowed-to-attend-matches-2363243For the upcoming PSL tournament, fans will be allowed inside the stadiums (up to 20% of the capacity).