Idiom request: Putting too much effort, but the return is so low that it was not worth the effort

Question

I am looking for an idiom.

You put too much effort, but there is so little gain that it would not be worth the effort.

Update: More specifically, some guy wants to save money and gas, thus he skips toll highway and take the free road. But the free road is longer, or congested that he ends up using more gas.

Answer 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.

Answer 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.

Answer 3

You could talk about diminishing returns.

This two-word phrase has two related meanings. One is a more formal economic meaning, where further investment in an enterprise is unlikely to produce proportional dividends.

In a more informal sense, the expression simply refers to what you mentioned in your question: there's too little to gain from the effort, to the point where it's not worth the effort.

The M-W dictionary alludes to both of those meanings with these definitions, even using the word effort in its definition:

diminishing returns
1 : a rate of yield that beyond a certain point fails to increase in proportion to additional investments of labor or capital
2 : benefits that beyond a certain point fail to increase in proportion to extended efforts

Wiktionary mentions that the phrase is idiomatic, while the Phrase Finder gives this note:

In common usage, the "point of diminishing returns" is a supposed point at which additional effort or investment in a given endeavor will not yield correspondingly increasing results. So, when you have reached that point, it's better to give up the endeavor.

Collins lists this example sentence, showing the phrase being used by a Glasgow newspaper in its more informal sense:

By becoming a pop diva again, she has revitalised a career that, in the mid-1990s, was an exercise in diminishing returns.

Answer 4

One possibly related idiom is "using a sledgehammer to crack a peanut".

Answer 5

This makes me think of something like "[you're] spinning [your] wheels," referring to expending energy that does not give the desired result, but it's something you'd spend energy on, nonetheless. I understand that you are looking for an idiom describing wasting one's time and efforts in a nul sum kind of way at best, so perhaps a phrase starting with, "Despite all [good] intentions, [the agent was not rewarded for these diligent efforts]."

or "In spite of all [good] intents and purposes...."

"Robbing Peter to pay Paul" came to mind for some reason, but don't get that meaning from what you've described.