Well bud, have you happened to take a look at my signature. Do you think I have those saws (and the ~15 others that I don't have listed) just for the heck of it? Growing up, all we had was wood heat and burnt about 8 cord a winter in an old Ben Franklin stove. I learned to run a saw when I was about 10-12 years old, and it was a Homelite XL-12 so there was no creature comfort to it. I grew up on a farm, and know first hand what it's like to spend 10 hours on a hay rack, then spend another 4 hours stacking in the barn. I have about 6 cord in my pile at home right now, 90% of which was split with a 13 lb monster maul. Shall I go on?? Moral of the story, I not only know what work is, I can probably work you into the ground and keep right on going. So you can shove your "doubtful" right straight up you a$$.
Now, to address your point about the CL seller. According to the original poster, the guy's "cords" are really not 128 cubic feet. If he delivers any less than 128 cubic feet for the $40 advertised price, than he is not delivering what he advertised...period. If he's selling a face cord, than that is what he should have put in his ad. Nobody has ever argued that the $40 is a bad price for a 1/3 cord; my only point is I don't agree with people not selling what they advertise.
The milk and raw chemicals you mentioned are both sold for a specific price for a very specific amount. Both are very carefully monitored to be sure the buyer is getting what they are told they are getting. Stocks and new vehicles don't have a specific weight or volume, but if the buyer doesn't know what they are getting it's their own fault for not reading the information that's always provided. Firewood is impossible to regulate as closely because neither weight nor volume is a perfect way to sell it. Weight isn't feasible because most sellers aren't going to have a scale, and if they did the moisture content would be a problem. Volume isn't perfect either, because there are inherent inaccuracies do to stacking. But, most states regulate exactly what constitutes a cord, and it seems to me a seller would want to abide by the law. Most do, but there are always those that don't and take advantage of people.