It plateaus. After tier six the evolutions cost the same. And you earn exponentially coin per evolution killed. But after tier six they stay costing 10m. On tier one it was 20+ restarts before evolving to tier two. I’m not on mutants without having actually finished all waves of age of world wars. It just stops. You earn 18m after killing the cowboys and you can evolve , I’m on quantum age and haven’t actually fought against the age of world wars faction. It’s a fun game and reminds me of age of empires but it’s not finished and it’s like the devs haven’t played their own game up past the first 5 tiers. Or something was missed causing the evolution to be the same price