Released on December 15: In September 2017, mailbox milk prices for the federal order markets reporting mailbox prices averaged $17.55 per hundredweight, down 16 cents from the August average and 45 cents higher than September 2016. The California mailbox price is calculated by the California Department of Food and Agriculture. Mailbox prices reflect the actual price dairy operators receive for their milk, hence the name mailbox price. Typically, they are released about 3-1/2 months following the month for which the prices apply. Mailbox prices are reported at average fat tests and reflect all premiums, as well as marketing costs, including hauling.