More than £110,000 was spent on the halted prosecution of an alleged IRA man over child sex abuse claims and related cases, Northern Ireland's justice minister said.
The Director of Public Prosecutions (DPP) apologised to Mairia Cahill and two other women.
Ms Cahill said she was raped as a teenager in 1997.
The attempted prosecutions of Martin Morris for alleged sex abuse and IRA membership - and four others accused of IRA membership linked to Ms Cahill's claims of a republican cover-up - never got to trial because the three women withdrew their evidence.
Stormont justice minister David Ford told DUP peer Lord Maurice Morrow the estimated cost of cases raised following the allegations totalled £110,390.
Ms Cahill said: "It is a hugely regrettable bill for the public but I do think it is necessary. They had to prosecute a case of child abuse and the other linked cases.
"It is unfortunate that as a result of their failings that the public are left to cough up for that."
Ms Cahill, 33, from Belfast, a grand-niece of prominent republican Joe Cahill, contacted police in 2010 claiming she was raped by Mr Morris in 1997 while a teenager.
She claimed republican paramilitaries conducted their own inquiry and subjected her to interrogation before forcing her to confront her alleged attacker.
Her allegations, highlighted in a BBC documentary last year, shone a light on how the IRA dealt with alleged sex abusers during a time when co-operation with the police in republican communities was extremely limited.
A review by the former DPP in England and Wales, Keir Starmer, said the Northern Ireland Public Prosecution Service's (PPS) handling of what were planned to be three separate trials had "let down" the three women.
Statistics from Mr Ford issued following a question by Lord Morrow showed, since 2011, £75,872 has been spent on legal aid surrounding the cases.
Legal aid is paid to lawyers to allow defendants to be legally represented in proceedings.
A total of £30,207 was spent by the Public Prosecution Service and £4,311 by the Courts and Tribunals Service.
Lord Morrow said: "I note over £30,000 is estimated to have been expended on prosecution fees and given the manner in which the case literally fell apart, I cannot fathom how that figure is justified.
"Nothing can now apparently be done to bring justice for Mairia Cahill and that in itself is a travesty.
"However the expenditure suggests there now needs to be an investigation to establish exactly what efforts were being made to attempt to bring prosecutions and if the fees were merited."
Starmer said errors made it "almost inevitable" that the women would pull out of the process.
After they withdrew their evidence, not guilty verdicts were returned for the five defendants - Morris, Padraic Wilson, Seamus Finucane, Briege Wright and Agnes McCrory - all of whom have strongly denied any wrongdoing.
Ms Cahill has said Starmer's report had backed her long-time insistence that PPS failings had left her with little option but to withdraw her evidence.
She said the defence had sought repeated adjournments during hearings before the stoppage of the case.
"Someone should review the amount of legal aid paid to the defence."
Starmer's review was critical of the PPS and the prosecuting counsel involved in the case. He cited delays, insufficient planning and lack of communication with the women as key weaknesses.
He also criticised a "significant" failure by the PPS to challenge a defence bid to change the sequence in which the various trials were heard.
The move saw the sex abuse case against Morris moved from first in line to last, behind the two IRA membership trials - the first for Morris individually, then a second for the other four accused of membership.
The North's DPP Barra McGrory QC has said he was committed to ensuring the mistakes made would not be allowed to happen again.
The alleged abuse happened between 1997 and 2000 when all the women were children. They all made statements to police in 2010.
After the three connected trials effectively collapsed last year, Starmer was asked by Mr McGrory to examine how the PPS handled the cases.
Ms Cahill has waived her right to anonymity.