Digital printing presses are being used in the printing industry since more than twenty years. However, digital printing presses have not gained popularity among offset printing companies. The minimum lot is critical to the initiation of the digital printing business. When introducing a digital printing press, a company compares the cost of use with that of using a conventional offset printing press. But sometimes decisions based on such a comparison may not necessarily seem valid. Furthermore, a digital printing press salesperson may not understand the fundamental components of the cost structure of offset printing. The first enthusiasm for the digital printing hits a wall and is depressed because of this miss judgment. As for a cost model, the cost structure of offset printing in printing companies is explained in this article. I would suggest that this model be used by vendors when proposing a digital printing press to printing companies. Therefore I wrote this article.