I doubt there is a cultural difference when the cost is small. When we invite our kids' friends to play golf or some other activity, we expect to pay. However, if we invite someone out to dinner, the expectation (always) is that each pays for themselves. If I am renting a vacation home and ask if someone wants to join, then if I expected them to contribute, I'd let them know. If we ask people over for dinner, we don't expect any contribution even if a decent amount is spent on food/drink. For out of town guests, we often pay for dinners, etc., but it is not nec expected, rather it is since they paid and spent the time to travel to see us.
For a large cost, I simply would have discussed who pays what beforehand. Hard to tell w/o knowing what was explicitly discussed. Does "under the premise" mean it was discussed, or do you mean "under the assumption"?
With all the qoutes, it is hard to tell whether it was presented a being a favor or not. Still, given the cost, I'd expect it to be discussed.
Hell, the Aussie could have thought the favor was the full deal.