A spokesman for the presidency defended the decision, saying MPs can not “use motorcycles” for travel.
Critics accuse the government of having rewarded the 400 MPs who voted two weeks ago for the extension of President Salva Kiir’s term until 2021.
The government says the elections can not be held because of the ongoing civil war.
More than half of South Sudan’s population is threatened by famine caused largely by the conflict between forces loyal to Kiir and his deputy, Riek Machar.
According to the World Food Program (WFP), the conflict has pushed 3.8 million people to flee their homes.
The people of Juba, the capital of South Sudan, have condemned the government for spending this money on cars at the expense of development projects.
“Forty thousand dollars per person is a lot of money,” a woman told BBC Newsday.
“The government does not care about the situation of the population, is it a form of corruption? Have they been given the money to silence them? She added.
Another resident said that some officials have not received salaries for four months and that the government should have used the money to pay these officials.
Presidential spokesman Ateny Wek Ateny told BBC Newsday that the budget has been budgeted and that it is “absurd” to say that the government is wasting money.
MEPs would repay loans over five years, just as they had repaid similar loans granted in 2005 and 2009 for the purchase of cars, the spokesman said.