rjdafoe said:
Console Video Games
DVDs
Cars to a Car Dealer
Not only that - Consider collectibles, like trading carts. Shops by the big booster boxes with a price tag of around 100$ (though as shop, they get them even cheaper). In the MtG case, one card is then 100$ / (36 * 15) = 0.18$ worth. Yet they sell singles (of rares) for 2+ $ - that's an increase of a factor of ten!
Why do they do this? To regain their expenses - the non-rares are much cheaper and are really worth next to nothing and don't sell.
Now you could say "that doesn't apply to Magic Items" - but it does: A merchant may buy five items - an axe, a staff, a sword, a shield, and a cloak - all of them magic. But now, he sees one adventurer group per town (and that's perhaps generous in a PoL setting). Good chances that none of these items are what the adventures really want (they usually want something specific, as random things are rarely useful to them - they have found random stuff all the time).
So let's say one of four of five adventurer groups buys one item. How does he recoup the loss, because the other items weren't sold on this trip? By making the price for the single sold item astronomically high.
Basically, they buy items without demand, hoping to find demand. Since they know that a good deal of the stuff will only be sold in some years (when a group finds one particular item exceptionally useful) or never, they have to sell the ones they do sell for higher prices - because they would be pretty poor otherwise.
Really, our modern economy cannot compared to that, because in a fantasy world as D&D, there
is no real market (except in the market on a market place sense) - not without better travel. If you have to compare, compare it to the black market for weapons - because only a specific clientèle wants these things and the outlets for buying and selling things are similar.
Cheers, LT.