“The lawsuit is raising awareness of the commodification of the whole thing, and that’s good,” said Sierra Poulson, 28, a lawyer in Nebraska not involved with the case, and a founder of the online forum We Are Egg Donors. “The guidelines are skewed toward the intended parents, toward the industry making more money and business,” Ms. Poulson said. “We’re in America — the market would take care of itself without guidelines.”

Ms. Poulson, a three-time donor, is an example of how the market works. She was paid $3,000 for each of her first two donations, in Kansas, but $10,000 in Chicago for the last. “The third time I donated, the only reason was for the money,” she said.

As women wait longer to start their families, and find their fertility has waned, the demand for eggs from young donors — typically, donors are in their 20s — has risen rapidly. Cancer survivors, older women whose eggs are past their prime, and gay and straight couples using surrogates to carry their children used donor eggs in nearly 20,000 monthly cycles in 2012, compared with fewer than 12,000 a decade earlier, according to the Centers for Disease Control and Prevention, which collects statistics on assisted reproduction.

While many other countries limit egg donation and the compensation that is allowed, egg donation is essentially unregulated in the United States. But in 2000, the American Society for Reproductive Medicine established the guidelines for how much women should be paid. They say that compensation over $5,000 requires “justification,” and that more than $10,000 is “beyond what is appropriate.” The amounts have never been adjusted.

The society argues that capping the price ensures that low-income young women are not drawn to donate by a huge payout without considering how it may affect their lives.