I was reading an article in Footprints #15, the Dragonsfoot OD&D/AD&D e-zine, called “Historically Resonant” Coinage for Advanced Dungeons & Dragons by Joe Maccarrone. Even though I'm leaning more towards OD&D than towards AD&D, it did get me thinking about coinage. I don't have a solid plan on how to handle coinage in the Nine and Thirty Kingdoms yet, but I have some inklings.
I had thought about moving from a gold standard to a silver standard before, not just for historical realism, which isn't a hard-core concern for me, anyways. I want to encourage a medieval feel, but I don't care about extreme historical accuracy. No, my bigger concern was that copper should mean more, and gold should mean a lot more. But since I'm not concerned with accuracy, one option is just to say that in standard equipment tables, read 1 gp as 1 sp, and 1 sp as 1 cp. Keep prices listed in cps the same, but increase the quantity purchased for that amount. Keep the treasure listings in modules the same, but switch to the 1 sp = 1 xp standard; this gives the party far more incentive to concentrate on getting treasure than on fighting monsters.
But on the other hand, I like having to not look things up, too. A simple formula, like the one I whipped up for rolling your own melee weapons, would be nicer. My quick and dirty solution: guess the weight of the item and add 1 for every adjective or special property to get the base cost for a wooden item. Double this for iron, bronze, brass, or copper; multiply by 20 for silver items, by 200 for golden ones. If the item is restricted or the knowledge to make it is rare, double or triple it again. This is the price in silver pieces; change it to copper for small common items used by peasants.
This won't give accurate prices that match the D&D or retroclone books, but they'll be reasonable enough for quick play.