tram Pferdebahn has RunningCost=2. Its road same spec'd counterpart Horses has =80.
And tram Pferdebahnwagen has RunningCost=0 !!!
Yes, but trams have a much higher speedbonus to start with. The actual income is lower than the carriage.
The road carriage is hauling 12 passengers for 0.83c/km at 25km/h with a 21km/h bonusspeed.
The tram hauls 40 passengers for 0.02c/km at 25km/h with a 25km/h bonusspeed.
That slight difference in bonus speed does not make up for 3x the capacity at basically free running cost.