figure on a whole day shot to take a load in, that is worth about 1/4 what you would get on a self loader, or straight truck.
$250-350 for each load of logs to the truck, depending on distance etc.
As for a goose neck behind a 3/4 ton, say they are legal to 16k ish, well the truck is only rated to 16k, including truck and trailer which add up to roughly 10,000# so you are only going to get about 6000# legally and safely on that trailer (hypothetical numbers here), and yes I've seen folks pull 16000# dozers with a goose neck and a dually truck, were they legal? maybe, were they safe **** no. bTW your argument of my truck has 700hp and 9000ft lbs of torque means **** all to the fact your brakes are still only rated to stop 16000lbs... get it?
Now figure on that board foot you are getting does not account for any waste, so saw kerf, bark, slabs etc. so go ahead and double the effective weight for every bf you get paid for.
3.42# per bf is a decent number to go with (average from the machinery handbook), 5000 bf would be 34200# yer truck rated for that?
To put this in real world perspective, the log trucks I use are rated for 88000 or 96000 depending on the truck and log lengths, they weigh in at around 40000, so they can get 48k or 56k pounds of logs, I have only seen a scale check over 5000 bf once, generally range from 3500 to 4500 bf, Keep in mind these are long logs, so add in taper across 36' or so... Taper I don't get paid for.
And to bring this back to reality, a pick up truck rated for 16000lbs towing capacity, with truck and trailer combined, a total payload of approximately 6000 is equal to right around 877 bf, at current Doug Fir prices (750 per mbf)...$657.00 of which you lost $100 in fuel, half to the owner... you get $278.50 for a long days work...