Public transportation costs vary between different public transportation options in Istanbul, however regular metro lines, bus lines, tram lines, funiculars, and cable cars cost around 0.50 euros per person per ride (50 euro cents). Prices change every year but they tend to stay around the same price range in euros or USD.
Ferries usually charge 15-20% more so a typical ferry ride from the European side to the Asian side of Istanbul costs around 0.60 euros (60 euro cents) per person per ride.
Ferries to the Princes’ Islands costs around twice the regular ferry fee so around 1.2 euros per person per ride.
Two exceptions are Marmaray and Metrobus lines.
Both Marmaray and Metrobus lines are extremely long, Marmaray line is the longest metro line in Istanbul with 76,6 km and 43 stops. Metrobus on the other hand is 52 km long and has 44 stops. These two massive public transportation lines both charge you three times the normal metro fee (the normal metro fee is around 0.50 euros so they charge you 1,5 euros per person per ride), however, they both give you the option to take some of your money back if you do not use the full length of the metro line.
Once you get off Marmaray or Metrobus, you will see people tapping their Istanbul cards on the refund machines to quickly get their money back to their Istanbul cards.
The logic behind this is to charge passengers who use those metro lines for shorter distances for less money
