“It is clear that it drives up the prices for these services and the commission system should be modified,” said Ryan Shapiro, the chief executive of JPay, which is based in Miami. Doing that, he added, can be difficult because many state budgets are strained.

Not that JPay is shying away from the business. It has deals in 33 states to provide money transfers, and contracts in 17 states to provide email, along with other services in states across the country. Now, it is offering a $50 tablet that allows inmates to download MP3s and get limited access to email, educational videos and books. The response from corrections departments has been overwhelming, Mr. Shapiro said.

The response from inmates and their families has been less enthusiastic.

Ely Peterson often wires a small amount of money each month to the commissary account of his fiancée, who is serving a 15-year-sentence at the Tennessee Prison for Women in Nashville for acting as an accomplice to murder. But transferring $25 costs Mr. Peterson $6.90. Mr. Peterson, who is 72 and a retired Marine, said that some months he can barely afford to send $15 to his fiancée, who uses her commissary account to buy food.

Walter Chruby, who has served 19 years of a life sentence for murder, calls such rates “unjust and unreasonable.” Mr. Chruby, 51, who is at State Correctional Institution-Laurel Highlands, in Somerset, Pa., argued in a lawsuit filed in federal court in Alexandria, Va., in April against Global Tel-Link that prisoners had no choice but to pay the high rates.

Mr. Chruby’s sentiment was echoed in dozens of lawsuits filed by inmates against Securus, Global Tel-Link and other providers. While the F.C.C. capped interstate telephone rates at 25 cents a minute earlier this year, after agitation from prisoners’ rights advocates, local phone rates can still be steep and other fees vary widely from state to state. For instance, using a phone to transfer $10 into an inmate’s account via JPay to the Southeast Correctional Center in Charleston, Mo., costs $3.95, while a similar transfer to the Illinois Youth Center in Chicago runs $5.95.

Placing a 15-minute in-state call from a Union County, N.J., jail costs $8.50, according to the New Jersey Institute for Social Justice, which recently filed a petition asking for lower in-state rates. In New York State, which does not accept commissions from providers, a 15-minute phone call costs just 72 cents.