NZTA performance manager Peter Connors told the Otago Daily Times about $1 million had been spent on manpower and machinery, $350,000 on helicopters, $250,000 on geotechnical and aerial surveys and pin placement, $150,000 on signs and traffic control, $106,000 on radio communications and $150,000 on abseilers.
There are about 10 workers on the slip site each day, including the three abseilers.
The cost has risen $500,000 since two weeks ago, when the NZTA reported it had reached $1.5 million.
Mr Connors and other NZTA staff were in Wanaka and Makarora yesterday to discuss the impact of the slip with neighbouring communities and tourism industries. About 12 members of the public attended in each town.
The NZTA had rescheduled the meetings after the slip closed the road and prevented staff attending the original sessions last month.
The road from Makarora to Haast has been closed every night from 6pm until 8am since the slip happened during a storm on September 10. Although significant rainfall in the area has also caused major daytime disruptions for motorists, the road has been consistently open all day for the past 12 days.
Mr Connors said the slip ''couldn't have happened at a worse place'', as it was one of the narrowest sections of the Haast Pass route.
Up to 40,000cu m of debris had come down, and rocks - some weighing up to 250 tonnes - took just 10 seconds to hit the road after they began falling.
The slip was ''cleaning itself out'' and was back to bedrock in a lot of places. However, the greatest risk was if it migrated sideways or above the head scarp.
Although the slip was continually stabilising and becoming safer to work on, night closures would continue until at least April, NZTA staff reiterated.
Work could hopefully then begin on a permanent solution, such as debris fencing or a debris catch area - which would require reshaping the whole rock face.
''We're stuck with this for some time and we can't make wild promises here that it's going to be any better so that's all we're trying to get across,'' Mr Connors said at the Wanaka meeting.
''This road economically, with an outage, is a significant loss to the economy and it's well recognised, so there's absolutely no [financial] impediment, but the problem is what's a practical solution? ... can you build it? Can you keep the road open?'' Residents called for the road to be open longer in the evenings during summer.
Mr Connors said the same message had come from Tourism West Coast and the NZTA was considering extending the opening hours, possibly until 8pm. That would require closures during the day instead, when contractors could work on the slip.
NZTA Otago senior network manager John Jarvis said high rainfall during winter and spring and a large number of tremors had caused new problems region-wide.
''There's widespread movement in a number of places and we just hope nothing more's going to come down.''
Although the NZTA was proactive in managing known sites of instability, the stretch of road between the Neck and Haast was particularly problematic.
''We've got numerous places along here that could go at any time.''
Lake Wanaka Tourism general manager James Helmore was among several people at the meetings who commended the NZTA on the good work it had already done managing the Diana Falls slip.
