That chart only works in a perfect world where all of our wages increased the same as inflation. If you account for all the downsizing and pay cuts that have taken place in the last 25 years we may be paying $5.00 or more per gallon(and I'm guessing here).
You are right. For me, gas is a hell of a lot cheeper now than it was back then. A quick calculation shows that I am making 7 times more than I did in the late 70s and gas is only about twice what I paid then in constant dollars. And I don't have any of those Jimmy Carter "odd-even" days to keep track off either.
Where do you get that from? Over the last 25 years real wages (wages adjusted to inflation) have oscillated up and down, but are currently about 4.2% less today than they were in 1980. That's 4.2% total, not 4.2% a year. (As a historical note, almost all of that drop occurred in 1980, real wages have been fairly flat since '81 and are actually a bit higher than the 25 year average)
On the other hand, gasoline (adjusted for inflation) has fallen by about 50%. It doesn't take a math genius to figure out that if you drop wages by 4.2% and drop price by 50%, you are paying substantially less of your wages into gasoline.