In my game accidentally noticed, that adding tram tracks to two specific road segments costs me negative (!) 2.15 billion. That’s right, after I built those my balance was like 4.4B. The screenshot with negative build cost is below (usually stuff costs some positive amount).
I noticed this bug while just preparing my road for intercity trams, and suddenly a lot of steam achievments got unlocked 😀
Is this a known bug/feature?
I can provide save file if someone (devs?) is interested.