Hi Blaine,
They show up on here now and then in the $4-5K range most of the time, and it depends a lot on what's with the gun.
Tripod, links, belts, belt-loading machine, optic rail, AA sights, spare barrels, tool-kit, ammo boxes, cases, transit chests, spare parts, etc. How much ammo do you have with it? Do you have a caliber conversion for it? (8mm vs .30-06 vs .308?) Do you have the jeep mount? Is it mounted on a jeep and you're selling the jeep and the gun?
The variety of 'stuff' that's out there for them is large.
The quantity of them in Canada is relatively small so that adds in a 'rarity factor' to the price point (my 'guestimate' is ~50 M-37's, and probably ~2-300 1919A4's, but someone else with more experience can chime in if they want to help on numbers.)
Because of the price of them, the market is also relatively small. How many people have that kind of money to drop into a gun, and how many have the money to feed them on a regular basis?
If you're looking to sell, do your research, and make sure you post some pictures of the package. That will help a lot.
NS