I was in Vietnam for seven months. I lived & worked in a city about an hour from Ho Chi Minh City for five months, & traveled for the rest of the time.
Unfortunately, I don't have accurate numbers for Vietnam, but it's safe to say that it was very very cheap. I didn't worry about the price of anything while I was there - I went on tours, ate out & traveled to my heart's content. I even went to Bangkok for a week without thinking twice about it.
By the time I got to China, I was in the habit of recording my expenses, so I know that I spent an average of US$45 per day there. Based on that, I can guess that I spent about US$25 a day in Vietnam - without even trying to save money. It's so incredibly cheap there.
I lived & worked in Shanghai for two years, where I rented a room from a Chinese couple for US$365 per month, which is on the cheap end of the spectrum. I went out about once a week & went shopping for clothing about once a month. I ate out for almost every meal - mostly at Chinese restaurants - but I ate at Western-style restaurants too, about once a week. My highest monthly expense was accommodation, followed by tourist attractions, then food.
Here's the monthly breakdown:
US$407 - Accommodation (including hotels on trips outside Shanghai)
US$296 - Tourist attractions (tours, museums, festivals, flights, etc.)
US$253 - Food (95% eating out)
CHINA PER DIEM: US$45
I traveled around the North Island for three months. I mostly stayed in free accommodation, either housesitting or Couchsurfing. I did stay at a few hostels along the way, so accommodation still figures in the top three expenses. My highest expense was food - even though I was careful to shop at the grocery store & eat at home. The next biggest expense was tourist attractions. Although I skipped the super expensive activities (skydiving was NZ$400!), I didn't miss out on the true once-in-a-lifetime experiences.
Here's how the monthly averages turned out:
US$379 - Food (90% eating in)
US$342 - Tourist attractions
US$232 - Accommodation (mostly free stays, or cheap hostels)
NEW ZEALAND PER DIEM: US$42
I was in Australia for six weeks, staying with friends in Sydney for most of that time. Australia is extremely expensive, so I was really mindful of finding free or cheap things to do while I was there. The last ten days of my stay, I "splurged". I went to four different cities, flying cheap airlines, staying in backpacker hostels & going on affordable tours. I definitely skipped doing things that I would have done normally because of the cost. I didn't go to Ayers Rock (US$1000 round trip flight from Sydney!), & I only spent a few days in each city outside Sydney. I just couldn't afford Australia.
Here are my average monthly expenses:
US$715 - Tourist attractions
US$611 - Food (90% eating in)
US$217 - Accommodation (10 days in backpacker hostels)
AUSTRALIA PER DIEM: US$68