A proverb meaning to make a profit with little or no expense or investment; to profit easily (lit. 'a monk earns pure profit').
あの商売はリスクがなくて、まさに坊主丸儲けだ。
That business has no risk—it's literally making an easy profit.
社員食堂を利用している社長は、会社の補助で毎日安く食べられて坊主丸儲けだと言われた。
They joked that the company president who uses the staff cafeteria gets cheap meals every day at the company's expense—an easy profit.
税制の抜け穴を利用してしまえば、坊主丸儲けのような利益が出るかもしれないが問題だ。
If one exploits a tax loophole, one might get easy profits like '坊主丸儲け', but that's problematic.