Portable fish finders range in price from just over a hundred dollars to thousands of dollars. Of course, most of the price is in the control unit. A large nine-inch touch screen display costs more than a two-inch screen. Adding an advanced sonar and premium navigation also increases the price. An advanced sonar will require a more powerful and more expensive transducer to send and receive the signal. Portable fish finders come with a carry case or shuttle and other accessories, which can add to the price as well. Manufacturers sell the case, display and transducers separately, but you can save some money by purchasing a pre-packaged portable bundle.