Walmart offers the Black & Decker 12" 20-volt Lithium High Performance Trimmer/Edger, model no. LST300, for $58.79 with free shipping. That's the lowest total price we could find $16, outside of the mentions below. It features an automatic feed spool, automatic line advance, and a 20-volt Max lithium battery that works with other tools in the 20V Max series.
A close price: Amazon and Target have it for $58.99, both with free shipping.