An extruder or injection molding machine with user-specifically monitoring and regulating processing of plastic materials includes a material feed, a plasticizer, and a mold. A process input variable, e.g. cost of the apparatus, raw material, power, and processed quantity, can be inputted with an input device and transmitted to a controller. A process monitoring variable, e.g. the duration of a product cycle, product cost, raw material used/power consumed per product cycle, expected purchase price for a given quantity of a product, and number of product cycles until maintenance, can be determined in real time from a process control variable and/or process input variable. A value of a process monitoring variable, such as the actual desired, or mean value, the value integrated since starting, the history or tendency of this value, can be outputted on an output device in form of a characteristic diagram.