Yes, I am an IATA graduated, and I can tell you that this the truth !!!
A one way is more expensive in the IATA publicated fares. This is technical a bit long to explain actually.
As I worked as Business Travel consultant, I often used the tactics like cross-tickets and fictive return tickets to get better fares. But this only applies to Corporate travel. And this can explain some no-shows on European flights.
Life is great at 41.000 feet...