The phrase "precios autos usados" means "prices for used cars" or "used car prices" in English. "Precios" is the word for price, "autos" means automobiles or cars and "usados" is the Spanish word for used and when combined can also translate to prices for second-hand cars.
This phrase is common when advertising used cars for sale or when visiting used car dealerships that want to advertise to both Spanish and English speakers. This phrase could also be used for an online search for cheap used cars available from Spanish speaking dealerships. Another word that means automobiles is "vehiculo" which means vehicles and could be substituted for "autos."