totally depends.
On...
where you are located
quality of the animal
condition of the animal
age of the animal
breed of the animal
gender of the animal
bred or not bred
registered or not
if the animal is in demand in your area
if the animal is readily available in your area
local market value of the animal.
you can find both goats and sheep in all kinds of price ranges.
you might want to start this query at a different point... perhaps...
what are you planning on using the animal for (milk, meat, fiber, weed patrol, grazing, brush clearing, showing, market animals)?
what kind of fencing do you have?
what kind of terrain and pasture/browse do you have?
what do you have experience with, or know people who have experience with?