Yeah, some persons noticed that. This upkeep is not justified, as Cultist is not an overpowered faction.

Off that seems like a huge penalty. Can you tell us anything else about the village? Was it under siege? Is it far away from your capital?

It's been awhile since I played Cultist are there improvements in the E&D influence wheel to offset that upkeep?

Perhaps it is also adding the upkeep of garrisoned units to the upkeep cost?

From my post in the Bug Report Forum: 

"I can confirm the bug appears in my games as well. 

The cause seems to be these lines in SimulationDescriptors[Class].xml which is located in Endless Legend/Public/Simulation: 

<!--Upkeep to pay per converted village when cultists-->
      <BinarySimulationModifierDescriptor TargetProperty="TotalCityMoneyUpkeep"     Operation="Addition"        Left="$(NumberOfConvertedVillages)"      Right="10"  BinaryOperation="Multiplication" Path="ClassCity,MainCity"/>
      <BinarySimulationModifierDescriptor TargetProperty="TotalCityMoneyUpkeep"     Operation="Addition"        Left="$(NumberOfConvertedVillages)"      Right="2"   BinaryOperation="Multiplication" Path="ClassCity,!MainCity"/>

It seems to be taking the normal upkeep and then doubling it; changing 'Right="10"' to 'Right="5"' fixed the issue for me."

This has been fixed on our end. I imagine it will be added on the next bug fix patch. Cheers!