While technology has made producing copies of digital content almost entirely free, there is no escaping that publishing, according to most definitions of the term, still requires time and money. Any publishing service offered by a library must find a way to achieve financial sustainability—that is, operate without losing money. However, even "losing money" is a tricky concept, especially when taking into account varying definitions of operating expenses (overhead costs) under different models for auxiliary services. Libraries are by their very nature cost centers, providing services without the expectation of recovering revenue, and are usually part of larger organizations that similarly provide services under partial or full subsidies. While libraries are often comfortable with charging for convenience services and for services to those outside their designed community of users, careful thought should be given to which costs a publishing service-or any new service-should be expected to recover.