The board shall fix, by official order, the minimum prices or a formula for the setting of minimum prices to be paid by milk dealers or handlers to producers for milk or milk components sold or delivered or made available on consignment or otherwise by producers to dealers or handlers: Provided, however, That the fixing of prices to be paid by milk dealers or handlers to producers for milk or milk components to be used solely in manufacturing shall be discretionary with the board.
31 P.S. § 700j-803