It's absolutely impossible go make even a wild guess.
Taking western europe as an example, there's a big difference between plopping in southwestern France for two months and leapfroging from Oslo to Palermo to Lisbon to Berlin to Dublin to ......
Transportation alone can dump your pocketbook.
Traveling in europe, I have no problem (when splitting with another person) getting by on a hundred bucks per person per day -- if we don't spend more than about twenty-five percent of the time in large cities. If I'm alone, it pushes $150 per day.
Southeast asia I can do on a lot less, if too many airplanes aren't involved. But I enjoy street food.
I've never broken the code on Australia and probably spend too much on transportation anyway. New Zealand is the less expensive of the two.
I bum off of friends in the Middle East, so no great opinion there.
You need to rethink in terms of spots instead of vast regions and work from there.