10 years old Die hard Gold

So, my Die Hard Gold 24 F battery cost me $80.00 after tax in 2009 therefore, it has a yearly cost of about $8.00. Current cost is $120. Doing the same math on a Red Optima, current cost $232 minus 50%, which should be the price in 2009 if compared to the Gold battery current increase, now we are at $116.00, divided by 15 years, equals a yearly cost of $7.73. Very close in bang for the buck if the 2009 price is accurate. See, math can be fun!