I was crossing overland from Peru into Bolivia about three years ago. They pulled me out of line because I was American. They took me to a back room and took my passport and the visa application (they had just started requiring it for Americans). I paid my $100 and they didn't want to give me back my passport until I paid a little more. The head custioms guy, an army official and the passport man all sat there making the money sign with their fingers. I emptied my pocket of any money I had (about 4 bucks in Peru money) grabbed my passport and left!