When it's a tenth of a toman.
The currency of Iran is the rial. At current rates you get about 40000 rials to a euro. That means you chop off five zeros and divide by four to convert prices. The really confusing thing is that most Iranians talk in tomans. One toman is a thousand rials. So you have to be careful how many zeros you truncate. Shops sometimes display prices in rials, sometimes in tomans. Even more confusing is that people in markets, for example, will give a price as "five" when they mean five thousand tomans, which is fifty thousand rials, or €1.25. Are you with me?
We had a bad experience tonight with a taxi driver. As usual, we negotiated a price before we got in (there are no meters): "three" (that's 3000 tomans, 30000 rials, about 0.75 euro). We arrived at our destination and presented the driver with the money. No! he shouted. He took out two 50000 rial notes and said "that's one, you owe me three!" He wanted 300000 rials, ten times the normal fare. We left the money and got out of the car. He followed us, gesticulating and shouting, explaining his case (apparently) to shopkeepers and passersby.
A few moments after arriving in our hotel room, the phone rang, but though I could hear voices, no one spoke. We went down to reception to see what was up. The crooked taxi driver had been in looking for us. We told the manager our story and he agreed it was an attempted rip off. We suggested calling the police if the guy came back, though I confess I didn't relish the prospect of an investigation. The driver didn't stick around long, but we wondered if he was waiting nearby.
(Sent from my tablet device)