I used a barter system for Omega World, a post-apocalyptic d20 game based on 3.0 D&D. The idea is that there is no "money" since things like clothing, food, shelter, water & weapons have utility that goes beyond fiat or specie. Trade goods could be anything valuable to a particular person or group, or not. I loved it because it removes the kill, loot, sell, rinse & repeat cycle. The players hated it--at first. They didn't feel like they "knew" what anything was "worth" (which was kind of the point). But, when they traded something "shiny" (a rolex wristwatch) to the king of the raccoon-men for his scepter (a vibro mace), they were happier about it. The key, I think, is to keep the player characters' items' power levels increasing as they increase in experience levels. I thought they would drop the flintlocks as they got shotguns, grenades & ray guns; but they didn't.
I think the way to do it for a fantasy D&D game would be to make magic items more rare. I would make them impossible to buy or trade. So, gold or money has no place in acquiring magic items. The spellcasters would be given access to item creation feats for free at the requisite levels. The key would be gathering fantastic components to make items. So, even 1-use items become special since you can't run down to the store and stock up. Permanent items are especially prized. Perhaps a powerful character could combine two lesser items into a single, more powerful item. Of course, the foes have to be largely stripped of magic, items especially, and something has to be done to make spellcasters more equal to non-magic-enhanced-non-spellcasters; perhaps a spellcaster only up half the total levels of a character. Again, these are just things I've pondered; I have no idea how they would play out. But I do think it would make magic feel more magical.