Drawing off a trend in the thread
Elves and Gondor,
there seem to be a number of goods/resources calling for
significant trade, and even movement of traders which in a
way echoes the Silk Route across Asia to the Middle-east.
Specialist wines (and there seems to be no reason this would
be limited to the wine of Dorwinion). Consider also tobacco, fine horses
for both carrying goods and riding (a prime resource for Rohan, with
the Rohirrim probably not be averse to trading a surplus of horses to
allies and friendly peoples- including Beornings), dwarf armor and
non military equipment. There would seem to be the basis for significant
trade, and if the economic return was high enough there would
always be people willing to dare trade routes, even across
South Rhovannion. Not unlike the Italian city states, they could charge
exorbitant prices partly because of the danger and scarcity.
Recall that elves, certainly in Rivendell, used horses. Surely they'd want to
have the best available (in Rohan- perhaps using Gondor as a middle-man
given Rohan's rather insular outlook). The Greenway would seem ideal
for pack animals and fast scout horses. And surely fast and war horses would
have been needed by Gondor when guarding the eastern and southern
approaches to Mordor when they were guarding the area.
Given that Tolkien noted in Letters that people were requesting more
information on various topics, and that obviously not everything can, or
should, be included in an adventure tale how much of a believable
economics and geography of trade routes can be fairly constructed?
One, I think, could involve tobacco, apparently overwhelmingly the best
being grown in the Shire, but used by at least Northern men and dwarves.
There could be a rather thriving trade across the East-West Road (when
orc and other harassment was contained) of Dwarf iron creations, hobbit
tobacco and food, men's food, cloth, and perhaps wine (by Dunedain
in the angle and Laketown?). With perhaps Elrond cutting some nice
middle-man deals at Rivendell's Friendly Trading Imporium Outlet
(somewhere on the road, not in Rivendell, of course

). On this route
sturdy ponies like Tom Bombadil's would probably be most useful.