Recipe: Jar of Yeast Culture

Crafting costs more than just buying from a vendor, which should not be the case. The produced number of Jars of Yeast should be at least 3 to offset the costs or wheat grain to flour should not be a 1:1 ratio.

Empty Jar = 2gp
Jar of Yeast = 20gp
3 Sacks of Wheat Grain > 3 Sacks of Flour = 8(*3) = 24 gp
Total production cost = 46gp

If you change the resultant product to 3, it costs 15gp per, rather than buying at 20gp.
If you change the wheat grain to flour from 1 bag of wheat grain = 3 bags of flour, that makes the cost 30gp, so there would also have to be a change in product ratio to 2 - making it 15 gp per.