For the actual difference then to now calculate the price then and now in 90% silver coinage...
For example: When silver dollars were still circulating, a gallon of regular at my local station was 19.9 CENTS a gallon.
According to Kitco, as I type this, silver is down to $20.75 per oz.
Make of it what you will, but when I graduated from High School, an ounce of 90% silver, $1, would buy you 5 gallons of gas. Today, an ounce of silver,$20.75, will buy you about 4 gallons of gas at the same station in my home town. The price per gallon, however, is now $5.38 gal.
(Interestingly, the price of a gallon of regular in my home town in SoCal, is just a couple of cents different from the price where I live now in Alaska.)