Those cars are NOT the DBRS9's. They are DBR9's. The DBRS9 is a derived from the DBR9, for private purchase (track days and such). However, Aston Martin has said that they are going to sell/have sold a few DBR9's (the full on race model) for private collecting.
You are correct, in that, they are around $320,000 to buy a base model DBRS9. I too would have one if I had the $$$. Build mine with the optional sequential 6 speed please.