Only “around 4%” of customers received a vehicle, the judiciary said, adding that a court found Ghaffari guilty of undermining the national economy.
The case drew more than 28,000 complainants and involved 28 defendants.
The judiciary said the court had sought to ensure victims were repaid.
“All necessary opportunities were given to the defendants to pay the people’s debts,” Mizan said, noting Ghaffari had claimed during trial he was ready to reimburse investors, which would have spared him the death penalty.
But despite “several warnings and deadlines” after the Supreme Court confirmed the sentence in August, he failed to settle his obligations, Mizan reported.
Judicial officials said the scam caused “severe financial and psychological harm” to victims, including stress-related illnesses and family breakdowns.
Iran applies the death penalty not only for offences such as murder and rape, but also in major economic and espionage cases.
It is the world’s second most prolific user of capital punishment after China, according to rights groups including Amnesty International.
-Agence France-Presse