KiwiRail thought it would cost nearly 50% more to build rail wagons in New Zealand than in China.
The decision last year to send the work to China ultimately led to 44 redundancies at KiwiRail's Hillside workshops in Dunedin.
A document prepared in August for KiwiRail's board and released to Radio New Zealand News following an Ombudsman investigation, reveals the higher estimate of the cost of building 300 freight wagons at Hillside.
Until now, KiwiRail has said the Dunedin bid was 25% - 30% more expensive.
The Rail & Maritime Transport Union says Hillside's price was not as high as either estimate.
Dunedin South MP Clare Curran says KiwiRail manufactured the figures for its own purposes.
But KiwiRail says it stands by the information.