The presiding judge, Marie-Elisabeth Bancal, described it as a "Machiavellian plot."
Picotin said the family's money was poured into a fake charity that Tilly, now 48, claimed was set up to pay the Vedrines' "protectors."
"He persuaded them they were surrounded by enemies," Picotin said.
With the trial over, Christine de Vedrines told the Sipa news agency the family would somehow rebuild.
"Eight years is a small price to pay for what he did to our family and children," said Christine de Vedrines, who Picotin said was locked up by the family for nearly two weeks and deprived of sleep and food before managing to get away.
Picotin said he hopes to help the family reacquire their ancestral home. As for the rest, he said, "it's all gone."
A Tilly accomplice, Jacques Gonzalez, was sentenced Tuesday to four years in prison.
Tilly's lawyer had argued that the family from the 13th-century village of Monflanquin in southwestern France had acted willingly.
"These 11 family members aren't ill, have their feet on the ground, a level of self-awareness. Eleven people manipulated by mysterious forces by a single man? The legal basis for the case is weak," lawyer Alexandre Novion told The Associated Press.
Novion denounced testimony about the family's mental state, saying a man's freedom should not depend on "an old Freud tome found in a psychoanalyst's attic." He also said Gonzalez -- and not Tilly -- was the ringleader and absconded with all the money.