3rd world people are not in the same boat, in Brazil a trip to NZ is a fortune, I've done it twice because of my job and for fun. It's one of the most expensive plane tickets you can buy here.
Flew to Auckland from SFO for our honeymoon for ~$950 roundtrip per ticket, so it's not horrendously expensive, but of course I'd hardly call that the kind of sum you'd want to throw away jut for an interview.
I know loads of tech workers who are still paying off their student debt/etc (or putting their kids through school) despite the relatively high salary.
Not if you're from India or Sri Lanka. Even though we could afford a round trip to NZ, but I wouldn't want to spend about 2 months of salary for an interview.