top rate is $1.50 per mile. uasally that is very high end. the normal rate is $1.25 for a reputable hauler that has all the proper insurances. there are guy's who do it cheaper but they don't have the proper stuff. so they have lower overhead. plus the diesel is so expensive now i have been charging normal rate plus an extra 50 - 100 bucks to cover extra gas.
in most cases even the most cut throat guy won't go under a dollar a mile. you bid even less which is fine because i assume you are doing a friend a favor. if he doesen't see it that way then he's not your friend. i don't think many people realize the reasponsibality and liability we take on ourselfs when towing there toy's.