The invention includes methods, systems and devices for authenticating transactions. A method may begin by enrolling at least two biometric specimens to a database. A false acceptance ratio ("FAR") is determined for each of the specimens, and authorization options are identified. A cost value is calculated for at least one of the options to provide a calculated cost value ("CCV"). The CCV may be a function of the FAR(s) of the specimen(s) corresponding to the option. An acceptable cost value range ("ACV range") may be identified, and compared to the CCV. If it is determined that the CCV is in the ACV range, then the option is selected. If the CCV is in the ACV range, then a set of biometric samples is provided (the "sample set"). The sample set is compared to the biometric specimens, and it is determined whether the biometric samples match the biometric specimens. If the biometric samples match the biometric specimens, then the transaction is authorized.