Ive found maintenance costs to be perfect in my play through , as it help identifies the most profitable roots in all areas and which trains i should be using for different jobs ect.
Ive had fluctuating profits from 28 to 17 million by late game due to experimenting with different train networks, this shows that trains do in deed cost ALOT of money but if you’ve set up to deal with the hit and miss nature of the business simulation side of the game its all part of the learning and mastery of this great game!