A method for routing electronic payment transactions includes receiving transaction-related information from a merchant, extracting transaction routing criteria from the received transaction-related information, dynamically identifying one or more eligible payment networks based on extracted transaction routing criteria, predicting a likelihood of authorization acceptance for each identified network based on the transaction-related information, dynamically identifying one or more breakeven transaction amounts for each identified eligible payment network, each breakeven transaction amount defining a point at which two or more eligible payment networks have the same expenses for a given transaction amount, the expenses including costs associated with a low predicted likelihood of authorization acceptance, and routing signature debit transactions from the merchant to a least cost PIN-less debit network selected from the eligible payment networks based on identification of a desired breakeven transaction amount for the PIN-less debit network.