労多くして功少なし (Rō ōkushite kō sukunashi)

Literally: Much toil, little merit

Example: “手作業で写真を一枚ずつ整理するのは、労多くして功少なしだ。” — Sorting the photos one by one by hand is a lot of work for very little payoff. The game isn't worth the candle.

English equivalent: The game is not worth the candle

Origin: Kō means achievement or credit. The earliest known example is in the Shoku Nihongi, an official history, in an entry for 737, where a plan is judged to be much labor for little result and probably not the best course. It is used both when results are poor and when good work goes unrewarded.