Apparently you have never priced a medium duty, as an FL can be had for slightly less money than a loaded Ram/Ford/GM!!
And not only that, but the medium duty will be working long after it is paid for, unlike the light duty truck.
They can tow more weight safely, are not maxed out on every tow like light duty trucks are, stop safer, and are a true heavy truck, not a light duty which is under built, but grossly over priced!!
A friend if mine hauled RV's, after a while, his 1 ton (not mentioning brand, no need for a war.) started costing him major dollars, made the profit margin slim, has looked at many medium duty trucks, seem to pencil out better over the ling haul.