The cost of federally registering a trademark is far outweighed by the benefits of doing so. A first-time applicant must pay a filing fee of $325 for each class of goods or services listed in the application. If you are filing an "intent to use" application (before the mark has actually been used in interstate commerce), there is an additional $100 fee. Renewal applications cost less. All fees are nonrefundable.
Make your check payable to the "Assistant Commissioner for Trademarks" and mail it with the completed application, including specimens of your intended marks, to: Assistant Commissioner for Trademarks, Box New App/Fee, 2900 Crystal Drive, Arlington, VA 22202-3513.