SYSTEM REFERENCE DOCUMENT 3.5
The most common coin is the gold piece (gp). A gold piece is worth 10 silver pieces. Each silver piece is worth 10 copper pieces (cp). In addition to copper, silver, and gold coins, there are also platinum pieces (pp), which are each worth 10 gp.
The standard coin weighs about a third of an ounce (fifty to the pound).
WEALTH OTHER THAN COINS
Merchants commonly exchange trade goods without using currency. As a means of comparison, some trade goods are detailed below.
In general, a character can sell something for half its listed price.
Trade goods are the exception to the half-price rule. A trade good, in this sense, is a valuable good that can be easily exchanged almost as if it were cash itself.