Regardless of whether it’s possible, the game clearly wasn’t INTENDED to be played without trains and it requires you to go out of your way to not use them. And I think people who complain that trains aren’t profitable at all should either turn their difficulty setting down or learn to play properly. That would be an actual issue if it existed, but it doesn’t. Most of the best games that I, and other people, love are not entirely 100% balanced, they have exploitable game mechanics in them and if you’re an idiot who wants to “win” an open ended game then sure you can go ahead and do stuff that is counter to logic and counter to the game design. But they’re issues that one never has to encounter at all unless one actually tries and I’m only against fixing them because it’s been my experience that companies tend to lose sight of what is actually fun about the game in doing so. If they can fix it in such a way that it doesn’t negatively affect those who aren’t deliberately exploiting the game mechanics then have at it, go ahead and fix it. Otherwise, learn some self control.
And yes, exploiting included game mechanics, what the hell else would you exploit.
It doesn’t “go out of your way” to not use them at all. You start with a blank slate. You can certainly only use trams and trucks for almost the entire length of the game. Its not like you have to go in delete a bunch of existing trains or disable them in order to not use them.
Trains aren’t balanced, full stop. Maintenance costs aren’t on par with the full cost of buying a new train. It doesn’t even make sense.
As far as exploits go, exploits in games refer to bugs or the results of unintended designs. Vehicles aren’t a bug (other than all the bugs related to vehicles like how they teleport around when you upgrade a road or lay a road or put down a stop, etc) nor does it seem the mechanics of vehicles includes anything unintended.
An unintended design would be for example the designers making a merchant sell product A in at a price of 2 with unlimited quantity and forgetting they had a merchant somewhere who would buy the same product at price of 3, which would allow the player to generate unlimited income through trading. That would be an exploit that wasn’t bug related.
as far as 100% balance goes, I’d settle for something about 0% which is what they have now.