This made me wonder whether potatoes are really this expensive in Australia? In the UK buying 2000 calories worth of potatoes from a major supermarket would cost the equivalent of AUD2.12 not AUD9.90 ...

Though by comparison rice gets you 2000 calories for AUD1.03, spaghetti AUD0.92, carrots AUD2.51, "pure vegetable oil" AUD0.059 so a more varied diet could be cheaper.

Actually I'd like to propose the carrot-only diet... Trying to eat 5kg of carrots a day is bound to make you lose weight, though your skin may turn orange ;)