Yes, these were a 1,000 factory option, I have the exact ones in the second craigslist add, the guy is asking 700.00 that is a little better than 4 or 500...
If you still have your car's window sticker, you might want to check that. I won't say you're mistaken, because the price may have been different in 2011, but in 2012 those were a $495 option (I have them on my GT) and they're also $495 on a 2013. Further, they're the same wheels that are included with the V6 Pony Package, which costs $995 -- and that's for the whole package, not just the wheels.
(Actually, even if you're NOT wrong, it doesn't matter because the $495 price in 2012-13 is what potential buyers will be looking at.)
2012 GT Premium Coupe | Performance White | 401A Charcoal+Grabber Blue | Comfort Pkg | MT82 | Boss 302 Shift Knob | 18" Pony Pkg Wheels w/Brembo Pkg Center Caps | Boss/CS Front Valance | Scott Drake 5.0/Tri-bar Fender Emblems | FRPP Strut Tower Brace | Redline Hood Struts | GT500 Rear Splash Guards | Rear Spoiler Delete | Sound Tube Delete