Mogilyansky, a car exporter and owner of a company that distributes fire-extinguishing equipment, said he had made a "disastrous decision" to go to Russia and have sex with the girls, two of whom were 13 and the other 14.
He said that it was "by far the worst thing" he had ever done and that "no words can express my sorrow" for the victims.
McLaughlin said Mogilyansky was truly remorseful but had committed a "grave criminal act."
"[The victims'] lives will be different because they were harmed by Mr. Mogilyansky," she said.
"Wealthy Americans who think they can shortcut child-sex laws by traveling overseas need to take note of this sentence," U.S. Attorney Michael Levy said.
Federal authorities have prosecuted more than 50 sex-tourism cases since passage of a law in 2003 that makes it a crime to travel overseas to have sex with underage children.
Mogilyansky, a father of three, has been in federal custody since his bail was revoked after his arrest last December. He pleaded guilty in April to traveling overseas for the purpose of engaging in illicit sex and engaging in illegal sex.
The feds and Mogilyansky agreed as part of his plea to a prison term of 78 to 97 months, within the sentencing range.
Assistant U.S. Attorney Michelle Morgan-Kelly argued for a 97-month sentence, noting that Mogilyansky had "devastated" the lives of his victims and had robbed them of their dignity. (One of the victims said in a letter to the court that her encounter with Mogilyansky had been her first sexual experience.)
Morgan-Kelly said Mogilyansky thought that Russia was a "free zone" for his illicit sexual encounters and that he would not be caught by the authorities.
Defense attorney John J. McMahon Jr., who argued for a 78-month sentence, said Mogilyansky's criminal behavior was an "aberration in an otherwise remarkable life."
Mogilyansky's wife said he was a caring father and husband. A psychologist hired by the defense said Mogilyansky was not a sexual predator or pedophile.
