A half a pound of meat is worth 3 silver pieces. The DMG does not say if this is cooked or raw/rare, but considering that it's in the Meals sections it's probably cooked with the profession cooking skill factored in for cost.

Here's the situation. A group of adventurers near Rel Astra in Greyhawk killed three dire rats. They have taken the rats to a small town (Oakhurst) and try to find someone who will buy the meat.