I have a save where the player has 3.8 million gold in treasury and earning 80 000 gold per turn on 100% research, with the new treasury upkeep he only earn 40 000 gold per turn. So I'd say it helps as it was the biggest expense for the player in that save.
When units get higher upkeep the more advanced tech that unlocks them, the expense side of things will start to even out the huge income possibilities in C2C, but I still think income has to be curbed some for late game, some buildings provide too much income at that point.