Here is a Holt's rep email response that I received from July 2022, see below.
Reads like 845 pounds plus, so generally 2000 CAD bucks after insurance, duty, tax, and storage?, plus the time and effort figuring out some additional logistics.
Seem to remember that price per gun was less on subsequent guns, maybe 400-500 pounds per after the first?
It would be great if there was someone Canada-side who had this figured out and offered the service with plainly listed fees.
Although I suspect that generally it would be too expensive for most importing scenarios.
Overall I found it cost prohibitive and not worth trying to figure out the unknowns either...
There was an interesting conversation on CGN a few years back in which someone relayed their experiences importing guns into Canada by themselves, literally by flying over, picking the gun/s up in person and bringing them back with them on the plane.
It sounded like the cheapest option, or at least price competitive!
I think that thread is buried somewhere in the 'Shows us your guns thread'??