Start at 18, I would pay no more than 20. I just passed on a '08 Adrenalin, 5k miles, sticker $35,500, for $26k. This '07 w/30k miles is worth a lot less.
This ST probably stickered for about 34K. It looks similar to mine. It is a later model '07 due to the roll down rear window. I would say 18 to 19k should take it home. Where did they get the purple color listed?