Hello! You asked when the Lacks family found out that people were buying Henrietta's cells. The Lacks family discovered the truth in 1973. On that day, Bobbette Lacks, wife of Lawrence Lacks, the oldest of Henrietta's five children, was visiting her friend, Gardenia. After lunch, Bobbette learns that Gardenia's brother-in-law works at the National Cancer Institute. He tells her that he has been working with cells from a woman named Henrietta Lacks in his lab for years. When Bobbette tells him that her married name is Lacks and her mother-in-law is named Henrietta Lacks, his curiosity is piqued.
However, Bobbette cannot imagine he is talking about her mother-in-law as she has been dead for almost twenty-five years. Gardenia's brother-in-law insists that the cells in his lab come from a Henrietta Lacks who died from cervical cancer in the 1950s. Bobbette is flabbergasted:
"What?!” Bobbette yelled, jumping up from her chair. “What you mean you got her cells in your lab?” He held his hands up, like Whoa, wait a minute. “I ordered them from a supplier just like everybody else.” “What do you mean, ‘everybody else’?!” Bobbette snapped. “What supplier? Who’s got cells from my mother-in-law?"
Also, when Michael Rogers, a young reporter from Rolling Stone, goes to interview the Lacks family in 1975, he comes to realize that the family hasn't been treated well at all. They had no idea what an immortal cell line was. Sonny, one of Henrietta's sons, said:
“I didn’t feel too much about the cells when I first found they was livin,” Sonny told me years later. “Long as it’s helpin somebody. That’s what I thought."
Things changed when they read what Rogers wrote in his article about their mother:
Cell lines are swapped, traded, forwarded, begged and borrowed among research institutions around the world. ... The institutional sources of cells now range from [government]- supported facilities like Nelson-Rees’s to commercial outfits with toll-free 800 numbers, from whom one can order, for about $25, a tiny glass vial of HeLa cells.
Hope this helps. Thanks for the question!