Why do you say that?
Regardless of what it is that someone is selling, if the item is in short supply and demand exists, then by definition it's a sellers market.
Currently this site has 45 Calis for sale. Only ten of them are Beaches.
VW Commercial have 35 used Calis advertised. Only 10 of those are Beaches.
Autotrader currently have 75 Calis for sale of which Only 17 are Beaches.
So whilst all three of these main California used vehicle sources have a combined 155 vehicles for sale at present, Only 37 are Beaches. If you then remove those older examples with high mileage and the number is considerably less. Of those remaining, how many are still in warranty with anything more than a fairly basic spec? I would suggest very few indeed.
So even allowing for the higher than usual numbers of used Calis being offered for sale, dealers and private individuals can ask good money for low mileage Beaches with a good spec. They are in short supply as are new ones.
Based on these figures there are currently three other Cali variants for sale for every one Beach!