Hosting the 2010 FIFA World Cup could cost South Africa $3.7 billion, according to the organisers.
Original estimates had been as low as $295 million, but costs have risen steadily.
In 2006, the projected cost of hosting the event had soared to just over $1.5 billion.
The country's Deputy President has warned that government spending will not be "open-ended."
A bigger building programme and rising costs for raw materials have contributed to the expanding budget.
New stadiums in Cape Town and Durban were added to the construction plans after the initial bid.
The government has also been using the tournament to help fund transport infrastructure and other services.
$2.5 billion has been allocated to infrastructure development.
But Deputy President Phumzile Mlambo-Ngcuka said spending could not be "open-ended".
She was receiving an interim report on preparations for SA 2010 from the country's sports minister, Makhenkese Stofile.
"This report shows that we have complied with every guarantee that we have made," Stofile said.
"We even went beyond that."
A major security exercise in Cape Town was completed on Tuesday, one of several due to take place in the run up to the World Cup.
Deputy Police Commissioner Andre Puis predicted: "from the security point of view, a very successful World Cup."
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