TRADEVALUE

The value command can tell you several pieces of information, as follows:
VALUE freight - tells you how much your freight carrier is worth (not the
    stuff that it's carrying, just the horse or wagon or mule).
VALUE tradegood - tells you how much one unit of a good is worth.
VALUE tradegood freight [packwith] - This will figure out how many units of
    a tradegood will fit into the specified freight carrier. If you specify
    "packwith", it'll pack that good "around" the other good, filling up
    the carrier with as much of "tradegood" as it can, then adding as much
    of "packwith" as it can. It'll then tell you the combined value of the
    goods.

EXAMPLE:
    VALUE tar covered salt
will tell you:
    A horse pulling a covered wagon can carry 8 sacks of tar packed with 9
    sacks of salt. We'll pay you 300,864 gold for that.

See Also: TRADING CATASTROPHE TRADEPOST FREIGHT