Experts say the vote would cost at least half a billion dollars.
A public vote on same-sex marriage would cost Australia $A525m (£275.5m; $396m), according to a new report.
Australia’s government intends to hold a non-binding plebiscite on whether to allow same-sex marriage – although a date is yet to be scheduled.
The Australian Electoral Commission previously estimated the cost of running the plebiscite at A$158m.
However, research conducted by accounting firm PwC said this figure was far too low, as it did not allow for “total economic costs”.
The report also claims that a stand-alone plebiscite on a Saturday would cost Australia’s economy $A280m in lost productivity.
In addition, the impact the vote and its result would have on the “mental health and wellbeing of Australian citizens” would cost at least $A20m.
Funding the campaigns for and against the proposal would cost a further $A66m, it said.
“The real costs to government, the economy and members of the community to hold a standalone plebiscite are more than three times higher than the numbers commonly quoted,” PwC Australia CEO Luke Sayers said in a statement.
“Total economic costs have not been considered before and should be part of the debate on the best way to achieve a resolution to this issue.”
An alternative option would be to hold the plebiscite at the same time as the general election, before next January, as it would cost much less at $113 million, or a vote in Parliament which would cost $77 million.
Experts have also pointed to similar campaigns in California – which cost more than $6 per voter – arguing that the money could be reallocated to other key areas.
Previous Prime Minister Tony Abbott had insisted that Coalition MPs would not have a free vote on the issue, and that a plebiscite was the only way to settle it.
However when Malcolm Turnbull took over as Prime Minister in November when Abbott was ousted, he maintained that a plebiscite would take place.
This is all despite a majority of politicians in Australia now saying they would vote in favour of legislation for equal marriage.