A couple things here–re: the Dwarves, as I read it, have almost always traded their skills for food (a la the dwarves that delved Menegroth for Thingol in Doriath) or traveled as merchants to sell the products they have crafted (as the great dwarf road of Beleriand, used for trade, and as the down-on-his-luck Thorin, who was traveling to peddle his wares around the time of the Hobbit, show).
As for Gondor, I think (as others mentioned) that we DO see a bit about the agriculture of the region–rich farmlands to the south, herders, etc.; plus the Pelennor Fields was not just a big lawn (unlike in PJ’s movie); it was an enormous semicircle of farm and townlands, filled with agricultural fields, pastures, and farmhouses (which Tolkien describes the orcs as burning down after they break through the Rammas Echor and beseige Minas Tirith).
The Rohirrim are clearly herders, and keep more livestock than just horses. I’m pretty sure that Tolkien mentions other types of farming there, too (though we don’t see it; after all, almost everyone has fled their homes by this point in the face of Saruman’s troops).
As for the Elves … well, in my opinion, half of Tolkien’s point with the elves is that everything with them seem magical; thus, they never set a table, they just clap their hands and a fully-laden table appears in the middle of the woods. Plus, they’ve got that whole talking-to-plants-and-animals thing, and probably just can tell trees to grow apples for them.
Quite true that the dwarves are depicted as trading for what they need. My point is mainly that this trade doesn’t seem to be going on at the scale one would expect, at least at the point in time when LOTR is taking place. One particular case is the recolinization of Moria under Balin. Where were the dwarves getting their food from? Trading with the Dunlendings? Seems unlikely. They certainly weren’t getting it from Lorien.
Balin & Co would more likely have been trading with the Beornings, who were apparently engaged in agricultural practices in the vale of the Anduin (i.e., right close by) and were on good terms with the dwarves.
Maybe, but the Beornings lived up around the Carrock, a good 250 miles from Moria and a lot further away than Dunland. I wouldn’t call it “right close by.” A bit of a haul, I would think.
Ironically, the Orcs are the only race of those three for which we are told where they get their food. In Return of the King, there’s a scene where Sam considers cultivation in Mordor a ridiculous notion, with an omniscient-author comment that Sam didn’t know about the vast stretches of slave-tended farms in the south of Mordor, by which Sauron fed his armies. And I think it’s fair to say that by the time of LotR, most of the Orcs in the world were on Sauron’s payroll.
On the issue of money, I think that the ponies in Bree are really the only reference we have in the books to amounts of money. Bilbo’s share of the Erebor treasure was enough to make him fabulously wealthy, the mithril shirt was worth more than the entire Shire, etc., but it never says just how many of those dragon-coins it takes to buy a bottle of Old Vinyards, or how many sacks of potatoes one could get for a silver piece.
Also, while the pony they bought off of Bill was scrawney and malnourished, it’s pretty clear that Bill (the person) was ripping them off. He was charging the going pony rate for a beast that, without their care, would have been soon for the glueyards.
