I would expect to pay at LEAST the top going price for a specimen, guided by condition, but most presentation rifles tend to have been kept in pretty nice shape, so that's a lot.
If you have just the rifle, that's one thing. But the critter brings its own story with it, names, dates, places and all. If you can unravel some of THAT, then you have what the ant-teek dealers call 'provenance'. Any presentation rifle can become the centrepiece of a fine display, all by itself... and I would certainly expect to pay something for an opportunity like that, perhaps as much as half again in most cases.
On the other hand, there is some weird stuff floating around. I knew Gerry Hart in Winnipeg, "The Man Who Won't Pay Taxes", actually wrote the book on his 46-year career of scrambling the minds of the folks at Revenue Canada. Gerry always had his picture in the newspapers holding a shotgun with which he was going to blast the "federal tax goons and &*&^% &^# $^&%@ *^". Once, I got a chance to hold the famous Hart Shotgun for a minute and I very nearly required a defibrillator... for me. The famous Hart Shotgun wasn't just some old hammer double that Gerry had got out of a barn; it was a highest-possible-grade handmade German gun with deep-etched four-blade Damascus barrels, acid-etched for maximum relief on the steel patterns, fully (and I MEAN fully) engraved, chambered for 2-1/4-inch shells and it had been swiped from the personal gun-rack of Reichsprasident Generallfeldmarschall Paul Emil Benckendorff von Hindenburg, of whom we all have heard. Without provenance, an amazing gun. With provenance, a true link with a very great man. How do you price it, either way?
Thinking on beat-up Adams revolvers, what's a pair of them worth? Custer lost a pair at the Little Big Horn. Make any difference to the price? You bet!!!!! And they have never been found, although I do have my suspicions in that department... more important for medicine than for money.
So they are still out there. Just have to run into them. What they're worth is anyone's guess.
But if I were offered something that I thought I could trace to anywhere except Bubba's Garage, I think I would pay for the chance.