Price is warehousing cost

 

Car sales by the million courtesy ZH.

The spikes are about means sudden inventory congestion or shortages.

Cars are unique. When sales are down, someone pays for extra lot space for excess inventory, and that inefficiency eventually gets priced. The same for shortages, you still pay for the empty lot. Inventory contango, the goal is to eliminate that, it is an arbitrage.

In general, I have no clue on how the auto market works, but mobility of the inventory to external storage is part of it.