Reporting in!
We are coming up to the end of a trip, and my partner estimates by the end of 143 days he'll have spent about 8000 AUD (or 6270 USD). I am a bit more frugal and my expenditure will likely be around 7000 AUD (or 5490 USD). These figures include flights as well as travel insurance and vaccinations, not just the usual daily costs of accommodation, transport, food, activities etc.
Our itinerary over the 143 days is: Australia - Malaysia - Korea - Japan - Hong Kong - Macau - Thailand - Malaysia - Australia. (With Australia being our home base, not one of the destinations.)
I haven't gotten around to adding it up but (for just my portion) I'd say flights cost me a bit less than AUD$1000, travel insurance just over AUD$300, vaccinations around AUD$50, leaving approximately AUD$5650 for everything else during the 143 days, i.e. AUD$40/day (or USD $31/day) excluding flights, travel insurance, and vaccinations.
Cost per day for Malaysia is the least, mainly because we were staying with my family for most, though not all, of the time, and also because it is cheap anyway. Next cheapest is Thailand. Korea, Japan, Hong Kong and Macau are the more expensive destinations, and among those I would say Korea is the cheapest and Japan the priciest, with Hong Kong and Macau somewhere in between, though I might need to confirm with proper calculations. But also we were moving around quite a bit in Japan, and not so much in HK/Macau. If we had stay put in just one city in Japan, it might actually be cheaper there than HK/Macau.
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A few years ago we did an itinerary of similar duration of Australia - Malaysia - Myanmar - Thailand - Taiwan - Malaysia - Australia and that cost us less because the destinations were cheaper, plus the AUD was higher at the time.