Or just set up a taxi next to it for 2.5x the price?
There's almost certainly a taxi next to it that only charges X, and all taxis are required to clearly post their prices in their windows. The taxi charging 3X is simply banking on the fact the enough people are operating with incomplete information and will just hop into the first taxi they see without fully understanding how the system works.
In the UK, taxi rates are regionally regulated, with local councils dictating the maximum fare (per mile, per minute waiting in traffic, etc). I thought this was fairly common (in first-world countries).
As a tourist flying into Sweden, it wouldn't have occurred to me that the fare would be unregulated, and that I would need to exercise caution when choosing a licenced taxi.
So... we got so used to being coddled we can't do the smallest amount of due diligence (per a comment above, "will just hop into the first taxi they see").
There's almost certainly a taxi next to it that only charges X, and all taxis are required to clearly post their prices in their windows. The taxi charging 3X is simply banking on the fact the enough people are operating with incomplete information and will just hop into the first taxi they see without fully understanding how the system works.