The U.K. and the United States have differing approaches, actually. Certainly in the United States it's difficult to argue that it's going to be a burden on publicly funded services, unless it's individuals who are very low income and who will be on Medicaid. In both of those cases that is left more to the equivalent of our visa officer's discretion and is done on a case-by-case assessment.
As for Australia and New Zealand, we do these comparisons with these large, immigrant-receiving countries that are like us. They also have a threshold-based approach, and the dollar values of their thresholds are remarkably similar to ours after you consider exchange rates.