In 1925, crude, natural rubber cost $1.12 per pound. Tires, at that time worked, but not very well, and would last no more than about 10,000 miles, a little more than a year of driving for the average motorist. If the cost of rubber was $1.00/lb., it would cost the owner about $200 per year to keep tires on his car. In today's money, that set of tires would cost approximately $1900!
From Frank A. Howard, Buna Rubber: The Birth of an Industry. New York: D. van Nostrand Company, Inc., 1947.
Cost conversion from the Consumer Price Index (CPI) Inflation Calculator