What system are you using? Because D&D breaks down if you pull the rug out from under its blissful unrealistic economy.
I'd recommend FATE 3e (Spirit of the Century, which has a free SRD and PDF, and Dresden Files, which doesn't have a free semi-genericized version, but is better written and has a magic system, although the magic is unbalanced), or Cortex RPG (generic system, just got it and I love it).
In any case, I'm guessing barter would quickly spring up. The ramifications of this would be similar to Emberverse, which due to a time distortion effect, suddenly has all industrial and modern era technology, plus steam engines, guns, and explosives, stop working entirely. Bows and crossbows would be highly valued, as would arrows and bolts, with axes, hammers, and knives being next most important, then swords too long to act as knives being least important but still valued.