Cargo insurance varies greatly depending on what type of cargo you insure and the coverage limit. You can see rates ranging from around $1,000 per year to several thousand.
This varies greatly but unlimited mile radius for 1 million liability is about 9k a year. Cargo insurance is a different policy and depends on what you haul.
To get the answer, you need to weigh your tractor trailer empty. When you get that weight, Lets talk numbers, this is wrong but it is a big example. If your tractor trailer is 35,000 pounds empty....
By the time you factor in everything, such as truck payment, fuel, insurances, tags, paying yourself ,and a myriad of other things, it runs between $1.35 and $1.50 per mile.
The tractor weighs 20,000 pounds, the trailer weighs whatever it weighs, and the maximum weight of a loaded tractor trailer with one trailer is 80,000 pounds.