The document dump on Friday has revealed the Government significantly underestimated the cost and demand of managed isolation and quarantine facilities during the COVID-19 pandemic.
When the system was first set up in early April, the Government budgeted $195 million for six months.
"Once the hump of repatriation flights are complete world-wide, international passengers numbers are likely to remain low for some months as countries, like New Zealand, will continue to keep in place restrictions to manage the virus," they said.
"This should start to release pressure on provision of accommodating or quarantining New Zealanders coming home."
But in the first two and a half months about $80 million had already been spent and now more than 31,000 Kiwis have already arrived back in the country.
The original budget had been based on projected arrival numbers of 190 passengers per day but at the peak in June, passenger numbers were averaging around 300 per day.
The Government forecasted around 18 hotels would be needed. There are now 32 in use across the country.
The budget has now increased to almost $500 million until the end of the year.
The documents also revealed the total cost for taxpayers to put up one person in managed isolation - an estimated $5700 for 14 days in an Auckland facility.
On Wednesday the Government announced they will be charging $3100 for managed isolation costs for Kiwis who leave the country after the end of the week then return, or people returning to New Zealand for a trip shorter than 90 days.
Each additional adult sharing the room would cost $950, and additional children - $475.
"We have carefully considered how to design a system that is fair on arrivals and not a barrier for returning to New Zealand, especially for those who might already be experiencing financial stress," the minister in charge of managed isolation and quarantine, Megan Woods said.
"We want to share the costs in a way that fairly reflects the benefits to both the New Zealand public of having such a robust system, and those who leave and enter the country."
But the charge is only expected to recoup a small amount of the cost - around $10 million.
Officials also couldn't say how long border facilities would be required but a "best case" scenario was for a vaccination to be developed and in circulation by the end of 2021.
