He ran a huge promotional effort through winter and bookings were heavy with more New Zealanders home and wanting to travel.
But with Aucklanders and Waikato people not able to travel, they have been refunding the full track price, which came to tens of thousands of dollars.
"We're pretty kind with that, and that allows people to take on the risk of making a booking in the shaky environment of Covid," Monk said.
"But with the restrictions in Auckland, we've had to do huge numbers of refunds, so it's pretty gutting really."
Monk said the worst aspect of the cancellations was that they were often made just two or three weeks before the walk was due to start.
"Those gaps are really hard to fill, but I get it, people were holding out hope because they didn't know how long the lockdown would go on for."
If things did not improve, this summer they would continue to lose money.
"We find it quite difficult to find ways to apply for funding from the government around it," Monk said.
"You've got people paying in advance, so we have money coming in, and then the money goes out as refund, so on the books, it doesn't fit in with the scheme of being able to apply for government resurgence funding."
It has been a similar story for Wairarapa's multi-day fully catered Tora Walk, which is normally booked out a year in advance, the Kaikōura Coast walk and the two to three-day Banks Peninsula walk near Akaroa.
Trisha Hewlett, from the Banks Peninsula walk, said Aucklanders were the backbone of their business, and the Auckland border had prevented Northland people from travelling too.
"Just for November, 40 per cent of our walkers have cancelled or postponed because they were unable to get here.
"The good news is 60 per cent of them have postponed instead of cancelling, so everybody's been really positive, they're saying 'it'll happen in the future'."
Even so, they had taken a financial hit, Hewlett said.
"However, we do know what our fixed costs are, we know how many walkers we need to cover them, the Banks Peninsula track has been around for over 30 years and it's been for all the ups and downs of all the different things that have happened in that time, and we're still going to be here post-Covid."
Kiri Elworthy, from Tora Walk, said they wondered if they should have cancelled Auckland bookings earlier so they had time to fill spaces.
"What we've found is we need a three-week lead-in to fill places. After all, it's a three-day experience - that's quite a chunk of time to take out of a busy life without some organisation."
Once they realised it was a longer term situation, they did start extracting Auckland and Waikato from the system earlier and filled some places.
"There are no Aucklanders in the booking system up until Christmas. We're fully booked once again," Elworthy said.
"January is a different story. We are still waiting to see what will happen there."
- RNZ