recipe ingredient multiplier

[momopirou]

Hello,

Most recipes have an ingredient count (left panel), but also a material cost (right panel).
My question is: why are this 2 values different? and can it be improved? I currently have a lvl 93 armorsmith.

for instance a chainmail requires 1 mail sheet according to the recipe, but material cost on the right says 4.5 material cost.

Thanks in advance.