The Ministry of Justice has released, under the Official Information Act, the final figures, which all up total $3,333,495.45.
The former Dunedin man was convicted in 1995 of murdering his family and spent 13 years in jail before being acquitted in a 2009 retrial.
Lawyer fees make up a large part of the costs.
They are not broken out for the original High Court and Court of Appeal cases, which together totalled $250,389. But the fees cost $1,778,583 (58%) of the remaining $3,083,106.
The last High Court retrial was easily the most expensive at $2,338,809, with lawyer fees costing $1,404,503 and disbursements the rest.
Disbursement cost can include research, investigators, DNA and blood testing, forensic expenses, court filing fees, witnesses' accommodation and reasonable living costs for legal representation, some general office expenses, agents' fees, and specialist reports.
Legal Aid Services director Michele McCreadie said the legal aid costs associated with the retrial, the second Court of Appeal, Privy Council and Supreme Court proceedings, were paid to the lead provider, Michael Reed QC.
Colin Withnall QC, of Dunedin, part of Mr Bain's defence team for seven years after the first failed appeal, said legal aid provided representation to those who could otherwise not afford it.
"When all this started, David Bain was a student . . . people simply can't afford the amount of money that it costs to do this."
While paid legal aid for two hearings before the Court of Appeal, Mr Withnall along with long-time Bain supporter Joe Karam, worked many unpaid hours.
"For all the years that Joe and I worked to investigate it, there was no state funding.
"Joe paid a lot himself in the early days but ran out of money."
University of Otago law professor Kevin Dawkins said even when you take into account legal representation, experts and preparation time, it "does seem a lot of money".
The information from the Ministry of Justice notes David Bain is not receiving legal aid to assist with his application for compensation.
This is being considered by a retired Canadian Supreme Court judge.
