It's just, I mean just possible to build up a war city around 100mill/hr. It requires a lot time, farming, playing the market and forest raiding. When built it'll have to offloaded pretty darn quickly too. I'm also willing to bet players with cities this size have an army of alts feeding it as well.
That said, I've seen enough in the game to know that the time required to do all that means more people will prefer to bot. Anyone that has armies much larger than that are being fed by accounts that have bots or are actively using them. Think about all those alt account alliances.
Evony has become a culture of breaking the ToS. It started with a minority who wanted to win at any cost, then snowballed with botting, multi accounting, noobing and finally account sharing. Neko's words ring true. cheating will beget cheating. If those few had stuck to the rules in the beginning rather than let greed take over, we all wouldn't be discussing this now.

