Amazon offers the Barska Pro Edition Metal Detector
, model no. BE11638, for $68.19
with free shipping
. That's the lowest total price we could find by $2, although most places charge $80 or more. It features two modes of operation, an adjustable 15.5" to 25" stem, 6.5" waterproof search coil, and more.
Update: It's temporarily out of stock, but it can be ordered at this price for delivery when available.