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NOTES ON SCALING OF RECIPE COST (last modified 2026-08-10)
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Recipe cost has been harmonized among several mods that I maintain, which are:

  Zithorian's Extra Storage Tanks For 2.0+ (v1.3.0+)
  Extra Storage Tanks: Tiny Storage Tanks  (v1.5.1+)
  Extra Storage Tanks: Steel Storage Tank  (v1.3.0+)

It has also been adapted to match the storage tanks in Krastorio 2, if that mod is installed.

By default, the total ingredient cost will be roughly scaled according to this formular:

  (Raw iron cost) = 45 * ( (1k units of volume) / 25 ) ^ (0.707),

where the last number is the inverse square root of 2, which means that the relative cost gradually
decreases with size.

The required amount of iron plates (and pipes) scales according to this formula:

  (Iron plate cost) = 20 * ( (1k units of volume) / 25 ) ^ (0.354),

where the last number arbitrarily is half the exponent of the first formula. It means that the
proportion of steel plates increases with size, but they never replace iron plates entirely.

With Krastorio 2 installed, small and large storage tanks are scaled according to these formulas:

  Small storage tanks: (Raw iron cost)  = 20 * ( (1k units of volume) / 25 ) ^ (0.707)
  Large storage tanks: (Raw steel cost) = 44 * ( (1k units of volume) / 50 ) ^ (0.674)

For large storage tanks, the required amount of steel plates (and pipes) scales according to this
formula:

 (Steel plate cost) = 24 * ( (1k units of volume) / 50 ) ^ (0.794),

which increases the proportion of steel plates & pipes to steel beams with size.

So by default, the cost of each storage tank should roughly be:

  Vanilla (reference):
    Storage tank       ( 25k):   45 iron plates

  Zithorian:
    1x1 storage tank   (  3k):  ~10 iron plates
    2x2 storage tank   ( 12k):  ~27 iron plates
    3x4 storage tank   ( 72k):  ~95 iron plates
    5x5 storage tank   (150k): ~160 iron plates

  Extra Storage Tanks:
    Tiny storage tanks (2.7k):  ~10 iron plates
    Steel storage tank (125k): ~141 iron plates

With Krastorio 2 installed (where 1 steel beam is made from 2 steel plates,
and these are each made from 2 iron plates), the cost should instead be:

  Vanilla (reference):
    Storage tank       ( 25k):   20 iron plates (small)

  Krastorio 2 (reference):
    Big storage tank   ( 50k):   88 iron plates (large)
    Huge storage tank  (200k):  224 iron plates (large)

  Zithorian:
    1x1 storage tank   (  3k):   ~5 iron plates (small)
    2x2 storage tank   ( 12k):  ~12 iron plates (small)
    3x4 storage tank   ( 72k): ~109 iron plates (large)
    5x5 storage tank   (150k): ~183 iron plates (large)

  Extra Storage Tanks:
    Tiny storage tanks (2.7k):   ~5 iron plates (small)
    Steel storage tank (125k): ~161 iron plates (large)

I end up using values which are the same, or are very close to, the above.