Yeah, but it's not like the drivetrain of an F150 is light. A fully dressed Coyote V8, 10R80, driveshaft, differentials, subframes, exhaust, gas tank (with fuel), radiator & supports, fuel lines, etc, etc add up. So the batteries weight 1800 lbs, but your also removing like 1400lbs of stuff. It's pretty likely that the Lightning will weight in at barely more than a hybrid F150, and the lower range F150s, when introduced, will probably weight the same as the ICE versions.

A little appreciated fact is that a Model 3 and a Mustang have the exact same weight ranges: the SR RWD Model 3 weights about what a ecoboost Mustang does, and a GT500 Mustang is actually about 200lbs heavier than a Model 3 AWD LR Performance.