OpenCms is free of charge as it is licensed according to the LGPL (Lesser General Public Licence). It can be downloaded, installed and used without licence fees.
In reality, the costs depend on the specific requirements of the project, especially in the areas of hosting, development and support. For many projects, OpenCms can be used with almost no development costs by using the Mercury template. However, For more complex requirements, external services or more in-house effort are required.