But the case has raised questions about whether these women have been exploited, or empowered, by this enterprise.
What happened in Cambodia?
For the past two years, dozens of women have been supplying their excess breast milk to a company called Ambrosia Labs.
The company has been processing and selling the milk in the US. It was marketed at US mothers who have problems producing milk for their babies.
On Tuesday, Cambodia imposed an immediate ban on breast milk exports, effectively ending the business.
It is unclear why it has acted now, although this follows recent bans on other controversial practices such as organ trafficking and surrogacy. Health officials said earlier they were investigating as "the product comes from a human organ".
Several countries run milk banks, where women can donate milk to needy babies. Breast milk is also sold via websites and private networks, and is a thriving niche industry despite some countries' restrictions.
Why is the case controversial?
Children's charity Unicef said the practice was "exploiting vulnerable and poor women for profit and commercial purposes", and said breast milk should not be commercialised.
Ambrosia had set up shop in Stung Meanchey, an area near the capital Phnom Penh and known for its poverty, and reportedly approached women in the area.
Reports said Ambrosia paid them the equivalent of $0.50 per ounce (£0.40 per 28ml), while selling the milk for eight times that price in the US.
Critics say the practice encourages mothers to sell their breast milk instead of giving it to their own babies.
With Ambrosia, "the women are paid by the ounce, so there is the pressure for them to produce and sell their milk... When you introduce a price tag, it creates an incentive", says medical anthropologist Aunchalee Palmquist.
She also says the women may not be fully informed. While they may believe they are selling excess milk, breastfeeding women usually produce just enough for their infant, so some may be unintentionally selling milk that their baby needs.
The alternative is formula milk, but in rural areas, where the majority of Cambodians live, a constant supply of clean water to mix with the powder may be a problem. Many would not be able to afford formula in the first place.
A large percentage of Cambodian newborns are breastfed, but this has dropped in recent years, and overall child malnutrition is still an issue, according to Unicef.
Ambrosia says they only hired mothers who had breastfed their babies for at least six months - the minimum as recommended by the World Health Organization (WHO) - and limited mothers to two submissions a day.
The WHO also recommends that babies be breastfed, while eating other food, until the age of two or beyond.
Is there another side to the debate?
Ambrosia has argued that it was "empowering" women, and claims it helped more than 90 families financially.
Speaking to media, the women said selling their milk gave them a much-needed stable source of income while enabling them to stay at home and take care of their children. They could earn up to $12 a day - a considerable sum.
"We are regretful that this trade has been banned. It had helped our livelihood a lot," one mother named Chea Sam told AFP.
An alternative would be working in factories or other employment with lesser pay and less ideal conditions.
"They may be working long hours and would be away from their children, so they would not be able to breastfeed them for long," says Annuska Derks, who has researched Cambodian women's issues.
Some mothers also viewed it as helping out other mothers. In several South East Asian societies, "breast milk plays a role in establishing kinship," says Professor Derks.
"It's like the other child is also our child," one mother named Khorn Vanny told the Phnom Penh Post.
The issue is thus also about the mothers' rights as women.
"As uncomfortable as this situation may be, at the end of the day it should be up to women to decide what to do with their bodies," says anthropologist Charlotte Faircloth, who has researched breastfeeding culture.
"It's a difficult thing to decide their autonomy for them, to say they are not educated or don't know what's good for them. There is a danger in sounding patronising.
"If the buyer and seller are happy with the process then we have to respect that that is their decision."
So should Cambodian women be allowed to sell their milk?
Dr Palmquist argues that the women "are impoverished and therefore living in an environment where their choices are constrained. So there isn't really a choice here".
"There could be many other ways to lift them out of poverty in a way that does not biologically exploit women", such as providing better education opportunities and jobs.
The government said on Tuesday in a brief statement on the ban: "Even though we are still poor, we are not so poor that we have to sell human breast milk."
What experts can agree on is that the transnational sale of breast milk is an extremely complex but growing industry and needs greater scrutiny.