I only have the English translation of this from a Korean client whose English is not very good. He is not happy with a service provider and used this phrase, is it a Korean idiom or expression?
This sounds like a phrase an older Korean would use, and my first thought is that it may not be about bread and bread crumbs, but rather about 떡 and 떡고물.
떡고물 is often used as a word like "bread crumbs" when talking about money.
Me: Hey mom, you won the lottery so can I get some money? Mom: 뭐, 떡고물이라도 떨어질 줄 아니? (What, do you think I will drop some crumbs?) Me: Our latest project was a huge financial success for the company, no doubt our CEO will give us a fat bonus. Coworker: 우리한테 떨어질 떡고물이 어디 있겠어? 다 윗선으로 가는 거지 (Where do you expect there to be fallen crumbs for us? Everything goes to our superiors)
This usage of 떡고물 is quite dynamic, so it can be used in many different ways. This makes it an "idiom".
An idiomatic phrase that is always produced in the same way, like "사자는 풀을 뜯지 않는다", is called a proverb.
I can totally see how an older Korean would use that kind of language to say something like "He is making 떡 and selling the 떡고물".
By the way for those readers who like "sources" and only trust experts and native Korean speakers I'm a tall white guy whose first language is English who has had 300 Korean girlfriends, so you can trust me on this one.
There is no known idiom in Korean for "making bread but selling the crumbs". I have asked dozens of intelligent, well-read Koreans.
I did find this.
“Breadcrumbing basically means not being super interested in someone, but continuing to lead someone on,” said Bela Gandhi, founder the of Smart Dating Academy and a dating and relationship expert. “It’s leading somebody on with no intent of following through.”
That could look like a few different scenarios: it might be an ex who continues to “check in” with you, but never goes so far as to suggest meeting up. It may be a guy that you’ve been flirting with back and forth, who will disappear for weeks, and then send an ambiguous “Hey, how’s it going?” text.
Being Led On
Perhaps your client read this and is extending the meaning to "being led on" in the business relationship with the service provider.