walmart sells em around 14 dollars.
Lowes and home depot anywhere between 14 and 39 dollars
Make sure u get a digital one and not an analog one
Also was the best 24 dollars I've ever spent... my gains are all set so that I actually know how much power will get back to my subs max. And i know how much voltage I'm running and my final impedance load... It has proven it's worth time and time again for me, get one