Medieval Japanese-style economies – at least from an upper class prospective – are barter-and-gift economies, with a thin gloss of coinage laid over them. However, given that merchants, ronin, peasants, and eta are perfectly valid character types, the need for some sort of guidelines on prices does turn up. Note that these are extremely general: prices vary a great deal depending on circumstances as well as on what, where, when, and who you are. That’s why the “price list” simply gives the type of coin involved: the actual cost will generally be 1-10 of them. Characters who want to deal in rare, exotic, or legally-forbidden items will want appropriate allies, contacts, or connections, knowledge of the underworld, and social techniques, as well as plenty of cash.
While real-world ancient coinage systems were rarely simple decimal systems, this one is (and pays only loose attention to the original relationships between coins) because Daikoku (god of farmers, wealth, and prosperity) is more foresighted about things like that then real kings and coiners were. Note that the “Koku” is actually a measure of volume in history. To accurately represent it as a unit of value would require a sliding scale, based on the years rice crop – such as was used in Land of the Rising Sun (Lee Gold, published 1980). However, for gaming convenience Bushido (Fantasy Games Unlimited, 1981, Paul Hume and Bob Charette) introduced the convention that one gold coin = 1 Koku, and I see no reason not to continue the tradition. Zeni (also apparently Sen or Fen), Bu, Oban, and either Ryo or Ryu are historical currency units, although the terms Hyakuryu, Ikusenryu, and Yorozuryu have simply been coined by adding appropriate numerical designations as prefixes.
Barter (usually a handful of rice or tea leaves, bit of spice, twist of sugar, etc): Small quantities of household goods, candles, snacks, cups of tea, and other trivia. In general, no one with the talent necessary to be a player-character should worry about this sort of thing. Villagers will provide basic hospitality to any religious or upper-class figure under normal circumstances and most other characters should either be in the company of such figures or skilled enough to manage.
Zeni: Enough rice for 3-4 days (1), tools, household supplies in moderate quantities, basic clothing, trivial gifts, prepared meals, a days service from a peasant, a night at a cheap inn, a blessing from a wandering priest, sutra charms, and generous donations to the destitute. Such items can be found in any village.
Bu: Missiles, knives, and peasant weapons, sake, mundane books and scrolls, furnishings, instruments, most “kits” (divination, tool, smithing, doctors, makeup, etc), writing supplies, minor gifts, a night at a good inn, hiring a peasant artisan or ronin guard for a day, a pipe of opium, the aid of a peasant mage, sending a local message, bottles of perfume, and dedicated religious services. Commonly found in larger villages.
Koku: One year’s worth of rice for a man (1), secondary military weapons, minor spells (from temples and/or ronin shugenja), court-quality jewelry, clothing, silk cloth, major gifts, alchemy lab, riding horse, a night and multi-course feast for a group at a fine inn, an evening at a geisha house, a massive iron ingot, items of jade, fine crystal, or other semiprecious stones, a month’s service from a ronin, rare herbs and antidotes, minor poisons, a flask of gunpowder, minor gaijin artifacts, wagons, small boats, arranging a safehouse, sending a courier or herald a long ways, a trained watchdog, a year’s services from a peasant, a shop, or a block printing press. Found in large cities.
Oban: Armor, war horses, primary military weapons, large houses, intermediate spells (from temples and/or ronin shugenja), a month’s service from an expert ronin, a hired assassination team, powerful poisons, a minor magical device, exotic big cats and similar pets, notable gaijin artifacts, imperial travel papers, trading boats, samurai stipends (effectively doubled with the expected support), modest shrines, a fine inn, hosting a court wedding or fete, a sizeable block of opium. Normally special-order.
Hyakuryu (minted as presentation-pieces only, otherwise only for accounting purposes): Watchtowers and strongpoints, large ships, modest temples, building villages. Note that items at this level and up are usually obtained through political positions, rather than by spending money – but the money is useful too, especially if you’re trying to rush the construction of something.
Ikusenryu (1000 koku, a theoretical unit only): Modest fortifications, small palaces, major temples, secret strongholds, and mercenary regiments.
Yorozuryu (10,000 Koku, a theoretical unit only): Major fortifications, fleets, grand palaces, cities, and armies.
Now, this doesn’t address the issue of craftsmanship. The prices are given for goods of quality suitable for upper-class characters, since that’s the usual stratum for player-characters. Not everyone demands that sort of thing.
Inferior goods of poor quality are suitable for slaves, eta, and other people on the very bottom of the social hierarchy. Move prices for such goods one level down the chart. Trying to do anything fancy with such poor goods is twice as difficult as usual.
Serviceable, but low-quality goods cost only half as much as usual. They’re suitable for peasants, peddlers, and similar types. Trying to do anything fancy with such goods is 50% harder than usual.
Ordinary Goods are suitable for everyday use by the upper class. No modifiers apply.
High-quality goods, suitable for use at court, by powerful lords, or by the truly wealthy, cost ten times as much as usual, moving one level up the chart. Such items normally look very nice and either offer some minor bonus or make it roughly 20% easier to do fancy things – whether that’s cook a splendid dinner or cutting off someone’s head with your superbly-crafted sword.
Goods of superb quality, suitable for use by emperors, merchant princes, and other mighty individuals, move two levels up the chart, costing a hundred times the normal price. They usually offer either a substantial bonus to their users.
Marvels of legendary craftsmanship are priceless, and are not normally available for purchase. Such items are pretty much exclusively the province of gifts, gods, inheritances, equally legendary craftsmen, and grants from mighty rulers.
Optionally, you can raise appearance by sacrificing function. Items can be purchased that look one category better than you’re paying for, but function as if they were one category worse than you’re paying for, can be purchased. Thus you wind up with clothing that LOOKS superb at a glance, but which functions as if it was or merely ordinary quality – perhaps allowing bothersome drafts which are distracting enough to negate the social bonuses you might expect to get from looking so good at a political function. Still, they impress the unaware very nicely.