So a few things to unpack here:
1.) Is Kevin's expensive? Yes. They are top-5 most expensive dealers in the country. Full retail and then some.
2.) The H&H sidelock double rifle. Is it any good? H&H *usually* made guns in 500/465 as it was their proprietary cartridge by necking down a 500NE and having a bore of .467", Joseph Lang invented the 470NE around 1904 and H&H usually did not peddle competitor's cartridges, preferring to offer their proprietary alternatives. The case indicates an H&H that was a 500/465. IF that is the original case serialized to the rifle, it means the gun was converted from 500/465 to 470NE. Of course that is devastating to value, especially if it was not re-proofed in London and of course the seller conveniently omits any photos of the proof marks. Then the question if it was converted would be "Why"? A.) The gun was converted in the 1960s-1980s when you could not find 500/465 ammo and they figured, eh, lets shove a .474" bullet down a .467" hole. If the bore wasn't shot out or lapped down, that could be a perilous to deadly issue for a shooter. B.) The other reason could be that the gun had a pitted bore, worn rifling, and a corroded chamber. A 470NE reamer would clean up the chamber and the loose/worn bore might measure after lapping/honing to be closer to .470NE bore dimensions. This is important to know because you want to always know how bad a rifle's condition WAS so as to not be deceived by how it CURRENTLY appears. (it currently appears beautiful / restored)
I've seen a lot of these types of Best Guns in the past. We're talking about new car money for a flawed asset. That's a serious consideration for a weapon of that price because its valuable for three reasons: 1.) It functions as a weapon, 2.) It's collectible, 3.) It's art. If the gun fails to be collectible (modified) and fails to be art (new restoration altered the original artisan's work) it is hell to sell. Whereas perfect functional art will have select bidders that vary from white collar upper middle class bidders up to billionaires, flawed art will have zero to one bidder from the uninformed class. You can own a boat anchor.
Examples of boat anchor investments I've seen:
A glorious H&H royal deluxe double that was in 240 Apex flanged. Reproofed in the 1990s to 6.5x64r. It was done because they couldn't find brass in 1994. Now its stuck as an obscure, faded away, flash in the pan cartridge made only by RWS. It WAS a $70,000 gun and it now failed to reach $16,000 twice at auction.
An extraordinary self opening purdey double in 360NE that was altered to be 9.3x74r. Same ruined story as the prior. It was a $60,000 gun, it is now a gun that cannot fetch $15,000.
In conclusion: Go big or go home. If you want to buy distressed best guns, know they are distressed and pay distressed prices with the understanding it is not a true collector weapon and the future market for your heirs to unload it is mighty thin. Alternatively, buy a truly exceptional, unmodified gun and pay the $70,000 it is going to take to get an example that would create a future bidding war amongst billionaires that want more pristine art on their walls when you're taking your dirt nap. (courtesy for your heirs and value for your dollars)
The H&H if indeed it was modified AND reproofed, I wouldn't pay more than $27,000-$35,000 for the gun. I'm sure Kevin's didn't either!