What did they cost you new?
How long have you had them?
What kind of condition are they in?
The tires are obviously fresh - Post a few pictures.
What else will they fit besides your car? (Include the bolt pattern and off set info to capture a larger segment of buyers)
Then charge what ever you need to get out of them - I don't think their is an exact science to pricing them - what ever the market will bear.
Of course on CL post them a little higher than your bottom line; because everyone barters on the price.
You might want to put them in the SS classified too - just to see what feed back you get.