[whall6]

There doesn’t need to be a connection between the purchase and sale events. Any marginal unit of inventory added to a market will place downward pressure on the price of that inventory (i.e., make it more affordable). The reverse is true for a marginal bid for inventory.

The effect is so minimal when you zoom into a single sale of one home and purchase of one condo, but in aggregate this causes real noticeable price movement.