Back in the 1970s, just after the 747 was introduced, PanAm sold a First Class Around the World ticket for $6,000. But they also offered a special First Class Standby fare for $4,000.
They gave you a book of blank First Class Tickets and let you write your own.
There were no maximum or minimum stays on the standby ticket, and First Class in those days was never full, so I never got bumped.
I usually took 2 or 3 of those every year, spending anywhere from one week to two months to fly around the world.
The frequent flyer miles really piled up quickly.
I have never experienced such an exciting vacation for such a small amount of money.