Game geeks, or maybe just game designers, apparently make extremely poor economists. At least, that's the conclusion any economically literate person would draw from the D&D rules and supplements. One of the most outrageous discrepancies involves the relationship between the price of a week's worth of standard rations and the rate of pay for mercenaries.
In basic Moldvay/Cook or Mentzer D&D, a week of standard rations costs 5 gold pieces. This is ordinary food, not preserved or otherwise specially prepared. In other words, it's the same basic fare that makes up the diets of peasants and commoners, as well as adventurers in the field. This means that the typical peasant must necessarily be able to produce, on average, at least 5 gp worth of value per week. Either he produces it himself directly in the form of food, or he produces some other good that can be exchanged for food or the 5 gp to buy food.
This is, of course, far from the reality of medieval Europe, where a single gold coin could keep an entire family fed for months. It's a far cry even from Gary Gygax's analogy of the campaign milieu to a gold rush boom town. A single peasant in an economy of 5gp weekly rations must produce roughly 271 gp of value per year just to eke out the most meager existence. A family of five, assuming children consume half as much as an adult, needs to earn the equivalent of 912.5 gp annually! And that's a family that would be sleeping in a lean-to in the field they farm, wears rags or worse, and can't afford to pay the taxes and tithes demanded by king and church.
While that's wildly out of scale with the real history of our world, it's not, in and of itself, economically absurd. It could simply be assumed that gold is vastly more abundant in the game world than it is here in our real one. To me, this feels way out of whack, and it raises some other questions about the relative supplies of other metals and resources, but as far as pure economics goes, it isn't a problem per se.
Now, though, consider the rates in the Expert Rules for hiring soldiers and mercenaries. The military service of an untrained peasant costs 1 gp per month. It costs him 5 gp per week not to starve to death. That 1 gp per month isn't just the peasant's take-home pay after expenses; that is the total cost to the employer of hiring him. That is the sum total of his compensation for the month. Even a heavy horseman, presumably a career soldier and an elite one at that, earns only 20 gp per month, enough for four weeks of rations - which, it hardly needs to be pointed out, leaves him a bit short for the month, and less than nothing left over for the upkeep of arms and mount.
Clearly, either the price of food or the price of mercenaries and hirelings, or both must be radically adjusted.
Let's see if we can work out something a little more balanced.
Let's say that a peasant can, in fact, survive on 1 gp per month. His family of five goes through 42 gp per year. That's still a lot more than historical reality, but it doesn't devalue the gold piece nearly as much as that 912.5 gp per annum subsistence. From that 42 gp must come food, clothing, and shelter, plus tribute demanded by crown and church. If we assume 10% for the church's tithe and 25% in taxes, that leaves our peasants with 31.5 gp to live on for a year.
According to the Rules Cyclopedia, an outfit of plain clothes costs 5 sp. We'll assume that a peasant can get by with two changes of clothes fora year, so the family of five spends 3.5 gp on clothing. Remember that even upkeep performed at home by Mother with needle and thread counts against the family's total output for the year - it isn't "free." That leaves them with 28 gp.
Let's assume that 8 gp goes toward upkeep of the family hovel and miscellaneous expenses - blankets, needles and thread, nails, candles, and whatnot. 20 gp left now, all of which can be devoted to the annual food budget.
After crunching some numbers, what comes out is a price of approximately 1.1 silver pieces, or 11 coppers, for a week of basic, no-frills fare. Frankly, this sounds eminently reasonable to me. A week's worth of iron rations shouldn't cost too much more than that, especially considering that the family must preserve so much of their food anyway, in order to get through the lean winter months. In fact, if anything a packet of hard-tack and salt pork should probably cost less than bread and roasted fowl, by virtue of the fact that the former is less appealing and the latter more perishable and thus more difficult to keep a supply on hand. Obviously, relatively well-to-do tradesmen and the like, as well as successful adventurers when they're not in the field, may choose a richer diet for themselves, but it seems reasonable that standard rations should represent a baseline of nutritional subsistence.
The prices of many other everyday items on the adventuring equipment list probably ought to come down as well. A small sack shouldn't cost a month's wages for a peasant, nor should a dozen large nails (i.e. iron spikes), half a dozen torches, or a ten-foot stick. But at least now that we know what food ought to cost, it's easier to from a reasonable idea of what those other goods should cost, too.
The equipment price lists in the rule books were obviously designed from a pure game perspective, not from one of medieval economic realism, but with the addition of Stage 2 and Stage 3 exploration (in plain English, wilderness and political/social) that discrepancy quickly becomes painfully apparent. Of course, since it is just a game, it's perfectly permissible simply to hand-wave the inconsistencies away, but if you like as much internal consistency and verisimilitude in your setting as you can get, adjusting the economy is worth some careful consideration.