From her job at a packaging factory in Chicago, Patricia Gonzalez cobbles together $70 a month to send to her mother in Guadalajara, Mexico, leaving her less money for groceries. In Boardman, Ore., Raul Esparza, a migrant farmworker, works as many hours as he can to send $50 a week to his children in Mexico City.


Both resent having to pay Western Union a $10 fee to send money abroad and an additional cut to convert dollars to pesos. But these charges have fueled the company’s record profits and made it a relative outlier in the financial services industry.


As billions of dollars in fee income has evaporated at the nation’s largest banks because of regulations passed in the wake of the financial crisis, the money-transfer industry has escaped the crackdown.


Soon, however, the companies, which are largely regulated by states, will be subject to new federal rules. Starting in February, they will have to disclose more to customers about transfer fees and currency exchange rates. The rules, part of the Dodd-Frank financial regulation law, will also require companies to give customers up to 30 minutes after a transaction to get a full refund.


But consumer advocates are raising alarms that money-transfer companies face fewer restrictions because the rules do not touch the pricing of services.


“You still have a situation where customers are subjected to these predatory products with no cap on fees or exchange rates,” said Oscar Chacon, the executive director of the National Alliance of Latin American and Caribbean Communities in Chicago.


Money-transfer companies say that they offer an invaluable service for customers who might not have access to traditional banks and who would otherwise have no way of transmitting money to their families.


“The money-transfer industry is very competitive, and consumers have a range of choices for sending money,” said Tom Fitzgerald, a Western Union spokesman.


Western Union, which dominates the money-transfer market, notes that it already discloses the amount of money being submitted, the exchange rate and the amount that the recipient will receive. It also tells customers that “in addition to the transfer fee, Western Union also makes money when it changes your dollars into foreign currency.”


MoneyGram, among the largest companies, said, “We believe the new rules essentially standardize across the industry our existing high level of disclosure, which should benefit anyone wishing to send funds.”


Mr. Esparza, who sends money to his children in Mexico City, said that the $10 fee would not be onerous if he were sending a larger amount, but that it seemed exorbitant for $50. “Western Union’s fees are just too high,” he said.


Ms. Gonzalez said that even though $10 might not seem like a lot, “In Mexico, that money goes farther.”


Aside from the transfer fees, Western Union and other similar services profit as they buy batches of currencies at a wholesale rate. The money-transfer companies do not disclose the spreads they benefit from when they set exchange rates.


“It’s a big profit center for these companies, borne on the backs of the people who can least afford it,” said Matthew Piers, a lawyer in Chicago, who successfully brought a lawsuit on behalf of Mexican immigrants against Western Union in 2000 that accused the company of misrepresenting exchange spreads.


Western Union did not admit or deny wrongdoing, but agreed to pay more than $400 million to settle the claims.


Referring to the money it makes off the spread, Western Union said in its 2012 annual filing, “we generate revenues based on the difference between the exchange rate set by us to the customer and the rate at which we or our agents are able to acquire currency.”


Western Union received $1.15 billion in so-called foreign-exchange revenue in 2011, up from $910.3 million in 2009.


For Javaid Tariq, a taxi driver in New York City who sends money monthly to his family in Pakistan, the exchange rate is particularly infuriating because of how much money he loses. When he sent $300 to his family in April, he received 89.2 rupees for every dollar, less than the 91.2 exchange rate that he checks each morning, he said. For his family, that means 599 fewer rupees, or more than a week’s salary in Lahore.


Frustrated, Mr. Tariq said, “They are taking this money from the people who can least afford it.”