Age of Origins Guide breaks down math on permit event that seems to be recycled monthly with a. Facelift for the occasion. The mechanics and pricing are all the same.

Each permit if you buy the daily 1 pack essentially costs .016 USD so you can compare that against the prices of any other items. I’ve found this is the absolute cheapest way to get warplane alloy.

The event lasts 4 days. For $2.99 and exchanging wheat or killing zombies you can unlock the 200 permit level.