Today, I realized that the Tokyo Metro fare from Tokyo station (Marunouchi line) to Omotesando (via Akasaka Mitsuke and changing to the Ginza line) is 190 yen, but the fare from Otemachi (one stop further away on the Marunouchi line) to Omotesando is 160 yen.

The reason (I assume) is that one can go from Otemachi to Omotesando via the more direct Chiyoda line, but still one can walk from Tokyo station to Otemachi and save 30 yen. Better yet, walk from Tokyo station to Nijubashimae (a short walk along the underground passageway between the two Marubiru) and take the Chiyoda line from there. Quicker and cheaper.

Any other examples of such arbitrage?