No, It does not mean trams have expensive running cost than trains. Trams with in-city branch lines (not inter-city) would huge losses if running cost of trams are increased (especially hard difficulty)
Maybe I misunderstood you, but currently it is exactly the opposite as you say. Trams have in all areas lower running cost than trains. My Point is that the distance between cities is to small. On most maps the distance between cities is as width as 1 city. – For example the distance from west border of city A to East of city B is as long as city A east to city A west. – Thats what doe not make sense in my opinion and make trams so over powered.
Tram = low investment (can stop on the road, does not need it own tracks etc), high acceleration, agile in cities, but capped at 60-80km/h (which is realistic, trams here in Germany are capped at max. 80km/h, usually 70km/h. only some Rapid transit lines have 120km/h with small modified vehicle)
in-game advantage: higher frequency: more passengers.
Train: lower running cost, lower acceleration, needs straight tracks (which makes using inside cities impossible), but a higher investment.
And private car should not be problem when you use train extensively for inter-city transportation. You even could destroy country roads to prevent private cars, but good ‘train’ lines even make only few private cars on the streets
I know. But I bet you can get even better results with trams, using trains only from 1950+.