...reminds me of a trip with a cab back in 2010ish.
Two friends of mine and i went from Kladno to Prague via cab - a 30km ride. Cabdriver told us what this will cost, we took the ride. Cabdriver went well under the speed limit on the highway and it was clear early on: this ass wants to scam us.
Once we arrive he asked for double the price he initially asked to get. We gave him exactly what was agreed upon at the start and he threatened to call the cops. We told him "good luck" and "fuck you" and let him scream at us while we disappeared into the crowds of the downtown area.
It has been for 50+ years. The taxi union (mafia?) is very strong. Their head is a well-spoken and criminal driver who gets lots of money for lobbying. They protest by deliberately causing massive traffic jams.
Just don't use a taxi in Prague, the other options are usually better.