Just try this in north america...

I went to potosi two weekends ago with Isabelle and Adhemar.
We met in the bus terminal, bought our tickets for 15 Bols. If you do the math, it´s cheaper to take a three hour bus ride to the next city in Bolivia than it is to buy one ticket for the metro in Montreal. (or the subways in NYC or toronto).
Well, it would have been 18 bols with the bus terminal tax. But we didn´t pay that.

While we bought our tickets Adhemar asked what colour the bus would be and surprisingly, in light of why he was asking, they told him, "azul".
One thing i´ve learned about Bolivia is people are less fascistic about making a profit than they are in North America.
We left the bus station, hung a right, and proceeded to hang out on a street corner. I was sort of curious what we were doing.
"...Isn´t the bus leaving right now?"
"Yep. It´ll come from over there."
In five minutes or so, a blue bus came along, and we crossed to the side of the street it was on. A bunch of people, mostly from the country, were doing the same thing.
The bus slowed down, i won´t exactly say it stopped, and about eight of us climbed on. This, i´m told, is how you take the bus the Bolivian way.

If only this would work for airport taxes...