Upvote:2
It's mostly fiction. It's hard to find a specific example where this would make a significant difference.
For example Bergen <-> Perth in mid February was about $1100 and Perth <-> Bergen was about the same with one decent option being about $40 cheaper.
There is always variability of flight pricing, so it's hard to do an Apples to Apples comparison. Prices depend a lot on season, day of the week, special events at destination or departure, convenience of the connections, supply and demand, competition and many more.
"Buying outside the country" doesn't matter much either. First you need to define what that actually is. Which country is the one you buy in ?
Typically none of these makes much of a difference.