The cost of a 300,000-word novel depended on many factors, such as the type of magazine, pricing, and the way it was serialised. If the novel was selected by the publishing house to be included in the magazine's serial segment, then a certain publishing fee would have to be paid. These fees might include printing, distribution, copyright, and other fees. In addition, they had to pay the author a fee to compensate for the author's creative labor. The fees for the serialisation might also include the editing, publishing, and review of the magazine. In the process of serializing, you may need to pay a certain amount of fees to get the readers of the magazine. The specific fees that need to be paid may vary according to the magazine. It is recommended to consult the magazine editor or relevant departments to understand the specific situation of the serial fee.