Pearl paid a hell of a lot more than 50 dollars for that tank of gas.

She also paid for all of the corporate welfare that the oil companies receive from the US government (taxpayers). She is paying through the nose for the wars and covert operations that the US government is waging around the world to secure sources of oil. She is paying the health costs that result from the toxins released into the environment by the use of oil as an energy source. She is paying for the costs to clean up the environment caused by the use of oil as an energy source.

I don't know how much the hidden costs add up to for that tankfull, but I'll hazard a guess that it's enough to put her off using gas forever if she knew the true cost of that tank of gas.