Idiom request: Putting too much effort, but the return is so low that it was not worth the effort
Solution 1:
"Penny wise, pound foolish" works because to save a small amount of toll money, they'd waste much more time which also has a monetary value.
Solution 2:
Kristina's answer is good. Another phrase that can apply is a false economy. From the Wikipedia definition:
A false economy is an action that saves money at the beginning but which, over a longer period of time, results in more money being spent or wasted than being saved.