Faolyn
(she/her)
Well, according to the FR Wiki, Naskel doesn't export iron. It exports caravan equipment, pelts, sheep, wool, barley, and beer. So why would a town export caravan equipment via boat?@Faolyn - ok, let's run through these.
1. I'm sure that local areas patrol their local area. I could easily see lots of roads leading into each major center. Totally buy that. And, I'm sure there would be some connection between each local network. But, again, why would I send iron from the Nashkel Mines through Beregost (overland of course) and then take it overland to Waterdeep and not put it on a boat in Baldur's Gate?
The PHB puts the cost of traveling on a sailing ship at 1 silver/mile/person. That says nothing about the cost the space for cargo. People on this reddit post did some math and probably the cheapest option was 4 cp/mile/ton, which sounds acceptable to me, but you know what--we'll dop it to 1cp/mile/ton for ease of math. If you're carrying animals, you also have to pay for their upkeep in addition to renting their cargo space. Boat tickets aren't free and it's unlikely that the merchants in a mountain town (pop 4.5k, 1.5 of which are rural farmers) that is many miles from a coast own their own boat.2. Why do you think a boat is more expensive than walking? It certainly isn't. There are very, very good reasons you ship by boat and not overland. But, beyond that, what percentage of the population of, again, say Nashkel or Beregost, ever goes to Waterdeep in any fashion? Walking or by water? Would you expect a significant portion of the population of Beregost has traveled farther than Baldur's Gate? Heck, what percentage of the population of Baldur's Gate do you think has traveled to Waterdeep?
The Sword Coast is about 700 miles long and 200 miles wide (according to World Anvil). By my own crappy measurements involving measuring with my fingers, Waterdeep and Baldur's Gate are about 500 miles apart. It's a nice round number, so we'll go with 500. It's late and I'm kind of tired and math is hard but I think that means that it would be 50 gp to travel there by boat. Per person. I don't even know if that includes food and drink, or anything fancier than a spot on the floor to sleep in.
And say these Nashkel merchants are carrying one ton of cargo--say, one ton of barley--they'd have to pay 5 gp for that. Now, there's no price for barley in the PHB, but wheat is listed at 1 cp/lb., and I did some checking and wheat is, in modern times, nearly twice as expensive as barley is. So the shipping cost for a ton of barley would be about 10 gp or so, so they'd spend basically all of that on shipping.
Walking is free. If you use animal labor, you still have to pay for their upkeep, but depending on the animal they can at least do a little grazing. You can do hunting and fishing along the way to offset meal costs, and if they sometimes camp out, then they won't be spending money on inns and hostels every night.
So what's more cost effective? Free walking, occasional stays at inns and hostels, and hunting or occasionally buying food, or a hundreds of gp spent on travel costs.
And what percentage of the population travels? Exactly as much as is needed for the game.
But! Here's the actual point. Someone from Nashkel isn't going all the way to Waterdeep or Baldur's Gate. Instead, they'd get on the Trade Road maybe travel 50-100 miles, stop off at the one or two dozen small villages that are along the road, sell off their goods, buy stuff that they can then sell in Nashkel and then go back home. The vast majority of merchants will do the same. Despite what you seem to think, most people are not going from Waterdeep to Baldur's Gate or Calimport. And nobody but you claimed they would be.
A collection of connected paths. You have a series of towns. A road goes from town A to town B, then from town B to town C, then from town C to... you should get the picture. What we have all been saying is that there was no highway commission that built a road from town A to town Z. Instead, all of the existing roads became, over time, one long route.3. Sure, the trade road might be a collection of paths. But, if that's true, then your whole argument about large amounts of traffic heading north and south overland kind of goes out the window.
I thought we were talking about merchants, pilgrims, and the like, not "average people".And, if I'm travelling form Calimport to Waterdeep, is there a reason I don't stop in Athkala or Baldur's Gate and get on a boat? Why am I walking the entire way? And, again, what percentage of the citizens of Calimport have traveled to any of those destinations? Do you think that the average person in Calimport has been to Waterdeep?
Anyway, those average people are going by spelljammer ship.