Big money...my son is in that biz. Years ago he hauled mining equipment out of the iron range in MN to Detroit where it got loaded on a ship and went to China ( where else?).
Those loads were in the 250,000 lb. range and paid around $40,000. Now he has been hauling wind turbine blades.
Big money for sure but you have to pay for permits ($10k and up), escort service and the like.