Why is this? Is this a Vanguard specific difference, or are Australian fees just much higher?
This is a Vanguard-specific difference in the sense that in the US, Vanguard is a leader in lowering management fees for the mutual funds that they offer.
Of course, several US mutual fund companies have also been lowering the expense ratio of their mutual funds in recent years because more and more investors have been paying attention to this particular performance parameter, and opting for funds that have low expense ratios. But many US funds have not reduced their expense ratios very much and continue to have expense ratios of 1% or even higher.
For example, American Funds Developing World Growth and Income Fund (DWGAX) charges a 1.39% expense ratio while their 2060 Retirement Fund (AANTX) charges 1.12% (the funds also have a 5.75% sales charge); Putnam Capital Opportunities Fund charges 1.91% for their Class C shares, and so on.
Many funds with high expense ratios (and sometimes sales charges as well) show up as options in far too many 401(k) plans, especially 401(k) plans of small companies, because small companies do not enjoy economies of scale and do not have much negotiating power when dealing with 401(k) custodians and administrators.