Hauling is free labor, I can't imagine anyone figuring in hauling costs into their economy...
I agree 100%. If you have any idle dwarves sitting around, then hauling is free. If you don't have any idle dwarves, then you need to quit atom-smashing migrants. Long hauls are not a big deal because it creates a pipeline. In the long run, ore arrives at the smelter at the same rate it is mined. Having 3 or 4 chunks of ore in transit at any given time is not a problem, assuming you have enough haulers.
Long hauls are not a problem, but long trips for your skilled workers can be. Keep input stockpiles right next to (or above/below) the shop. This reduces the time your skilled worker has to spend getting the inputs. Not only does that tie up the worker, it also ties up the shop. Output stockpiles can be as far away as needed, since that just ties up haulers, which are cheap and plentiful. Have "hauler stockpiles" near the shops, so there is minimal delay from when an item is made and when a hauler arrives to clear it out to avoid clutter.
A "hauler stockpile is a dining/meeting hall with food and booze stockpiles handy. A hauler can bring a chunk of ore to the stockpile next to the smelter, then if he has no job he'll wander to the nearby dining/meeting hall to sit around. When the smelter has bars ready, he'll get off his butt and haul them to the bar pile next to the forge, then go back to the hall to wait until weapons are done. At that point, he's still close by so he can immediately haul them upstairs to the weapon stockpile near the depot & barracks. Items never sit still for long. Shops never sit still for long waiting for the skilled worker to collect inputs. The only thing that is ever idle is the haulers.
On the other hand, trying to maximize efficiency and put every dwarf to work will just give you ulcers, and you won't be able to buy any more from a given caravan because you can already buy everything. All it will do is make it so you have to give the caravan a few hundred percent more profit. Yes, I say "have to" because you don't really want all those extra widgets sitting around dragging down your FPS. Once you're making enough widgets to buy everything you need/want from the caravan, excess production is actually more harmful than helpful.