I think
City of Brass has a very real cost; the fact that
Mana Confluence is being used sparingly in Standard right now while painlands have been more widely adopted should attest to that. For cubes that are heavy on fetches and shocks especially, players quickly realize there's something of a hard limit as to how much damage you can take from your manabase. For what it's worth, City routinely goes unpicked from our utility pile over here, whereas
Evolving Wilds is almost always taken, despite about half the decks being three colour.
And yeah, I'm aware that Jason claims that City is worthy of a spot in his main cube list, and is a fairly high pick. But we never agree on anything else either, so.