How building costs and time scale

Below Furnace level 30, every upgrade draws on the four standard resources — meat, wood, coal and iron — with steel entering the mix at the highest levels. From Furnace 30 onward the buildings move into Fire Crystal tiers FC1 through FC10, which stack Fire Crystals on top of the usual resources. Build time rises with each level and is then divided by your construction speed bonuses and paid down by speedups, so two players with the same building can face very different real timers.

Costs climb steeply rather than linearly, so a single upgrade near the top of the standard range can demand many times what an early level cost, and the FC tiers raise the ceiling again. Because the calculator adds up every step in your range, entering a 1-to-30 jump shows the complete stockpile you need to reserve rather than only the last level's price — useful for knowing whether to farm resources or start refining Fire Crystals before you begin.