We pull our trailers in the marshes and rice fields where our cattle are.  I just put 6 toyo m/t on my dually for $2500  My buddy just put Interco m16 on his dually for $2200.   ALL of our pulling is down mud roads, flooded fields, and the coast of Louisiana.  Down here, a dually is the only way to go.  Those two extra tires help the truck "float" in the mud.  We all have wider dually tires with spacers to help hold the weight.  I know we dont deal with snow and rocks alot, but if we didnt have 4wd duallys, we wouldnt get anywhere.   In fact the dealership by my house hasnt sold a 2wd dually in 3 years.