Only the Breast, with 45 million ounces of milk coursing through its classifieds at any given time, has become a virtual bazaar connecting mothers who are unable to breast-feed with mothers who have excess human milk. This free-market model has wedged itself between traditional nonprofit human milk banks, neighborhood milk-swapping sites and the newest bio-science companies looking to make a killing from baby’s first meal.

Julia, a 22-year-old mother of a 2-year-old and 7-month-old in Fort Worth, Texas, says the site has been a financial blessing. “I’m a stay-at-home mom,” she says. “The extra money lets me feed my family an organic diet and sign my daughter up for dance classes.” As “Organic-Dairy-Soy-Gluten Free Mommy,” she sells her excess milk for $3 an ounce. (Julia and the other lactating mothers Newsweek spoke to asked that their last names not be used because they did not want to be judged by some friends and family members.)

Julia pumps 60 to 70 ounces a day; after feeding her children, she usually has 20 to 24 ounces left over, which she freezes in sterile, plastic bags. Once she connects with a buyer, Julia ships her milk overnight in an insulated cooler with dry ice. To date, she has sold over 1,000 ounces.