The Polestar 3 will debut in October. The announcement came buried in Polestar’s first-quarter 2022 sales release. Set to be built in the U.S., the Polestar 3 will take on the Porsche Cayenne. One of two 1955 Mercedes-Benz 300 SLR Uhlenhaut Coupes sold for 135 million euros ($143 million at current exchange rates). That makes it the most expensive…