Craft menu then resources you can check cost and calculate
Z / x * 4 = price for eu trader to fill contract
Z being quantity of resources. Eg 4x oak logs
x being gold cost. eg 292 to make 4 oak logs
4 / 292 * 4 = 292, so need to put contract on oak logs at 292 for eu trader to fill
someone with better #math could probably explain easier, not at pc so dont know if oak logs are 292 but i use this formula