There are a total of only 12 Sky's listed for sale on AutoTrader in the US, and almost all of these are new cars from dealers, probably just trying to get their name out there ... I don't think that's too many. For comparison, there are 86 BMW M5's, which only recently became available... and that's an $88,000 car !
Many dealers have their inventory auto linked to Autotrader. When a car is invoiced to the dealer it automatically will be shown on Autotrader until such time as it is delivered to a buyer. My Solstice was listed on Autotrader for about a week, even though it was still in shipment and was presold to me.