To examine prices over time, the U.S. Bureau of Labor Statistics (BLS) has Consumer Price Index (CPI) data going back to January 1913 and a few average prices going back to at least that far.
Here are some other interesting facts of changes...
By 2013, flour had replaced potatoes as the cheapest item per pound among the items tracked. And while potatoes remain among the cheapest food items today, potato prices have increased over 39-fold since 1913, the sharpest rate of increase seen of the items tracked over the past century.
Of the items listed on a per pound basis, butter was the most expensive in 1913, selling for slightly more than 40 cents per pound. By 2013, prices for coffee, steak (round and sirloin), chuck roast, bacon, and cheese were all significantly higher than butter.
Of the average price items listed, egg prices have increased the least, up about 5-fold in the last century, as advances in production, delivery, and storage techniques have outpaced those seen for most other food items.
To read more, go to: http://www.bls.gov/opub/btn/volume-2/average-food-prices-a-snapshot-of-how-much-has-changed-over-a-century.htm