my 750 gets 6.5 to 7 mpg. just for fuel I'm looking at .55 to 61 cents per mile figuring $4 per gallon. the truck costs $80k new and my insurance runs about 42k per year. then there's the op costs for maintenance.
generally,I charge $75 a load and I haven't had any probs getting that. tandems and bigger aren't getting much more here.