This article compares the costs of deacidifying a book in the Library of Congress mass deacidification system at its start up and full production output rates, in the Wei T'o pilot plant Nonaqueous Book Deacidification System operating at the Public Archives of Canada, and in the manual spray deacidification developed at Princeton University Libraries using Wei T'o solutions. The formula for calculating costs is described. The total calculated cost for deacidification treatment are lowest for the Wei T'o system in Canada. -- SCMRE