Palladium, Rhodium and Platinum are used for car exhaust catalyzers. Despite its superb heat and wear resistance, Platinum use is not overwhelming. Traditionally it has been used mainly for gasoil (Diesel) engines. Low Platinum prices have led to designing-in platinum/palladium alloys for regular gasoline engines. New designs take time for approval and in the mean time the electrification of the car fleet is getting traction ... Yet Platinum also is the only PGM metal with a meaningful industrial demand outside the car industry.

This is the main idea on Platinum in this article on PGM metals and silver. Plenty of graphs, both USD price and Gold to PGM-metal ratios.

Deflating speculative bubble of catalyzer precious metals