Think the most expensive place I've found is Cask in Pimlico
CASK Pub & Kitchen
They had an Imperial Stout for something like £14 a third of a pint. Just looked at their latest beer list and they have Ale Apothecary from Oregon for a whopping £69 for 750ml
And no I didn't pay those prices, really wanted to try the place out but as I got close decided to go to the good ol' Jugged Hare up the road and a pint of Fullers for much less.
The Cask Beer Kitchen have cask ale at around the same price as a pint of Fuller's anywhere else. If you were drinking London Pride, that's 4.1% ABV, if the ale Apothecary beer you're talking about is El Cuatro, it's 10.58% ABV, so there is a big difference in duty alone. The cost of fermenter space on a strong beer is more. Most of Fuller's is probably knocked out pretty quickly.
Have you though about economy of scale? How many tons of malt and hops are bought be Fuller's and how many thousand barrels of London Pride are brewed every week compared to a small brewery?
Fuller's brewery wil be fairly industrialised, the beer aged (if at all) in stainless steel tanks, whereas El Cuatro is afed in wooden barrels. In many US states, to legally sell your beer outside of tour own tap room, you have to sell through a distributor, so there's someone else taking a cut (though to be fair, I don't know if this applies to exporting outside of the USA)
Then there's import duty to consider; also transport. How did it get here? Was it sent by ship, or was it flown in to avoid the chance of it sitting on a dock in a metal container getting alternately hot and cold and damaging the flavour?
Finally, how many barrels of a well know beer at 4.1% ABV is a pub likely to get through vs bottles of 10.58% ABV beer? The pub will need to factor in what that beer is costing them to sit there until it's sold.
Sorry if it was not your intention, but it does sound as if you were saying that the Cask Beer and Kitchen is an expensive pub, whereas the Jugged Hare is cheaper and better value.
I've never been to The Jugged Hare, but have been to the Cask Beer and Kitchen and yes, they had some very expensive beer, didn't I think it an overly expensive pub.
Similarly, I've drunk London Pride and enjoy it greatly, but would never pay anywhere near £69 for 750ml of it. I've not had any of Ale Apothecary's beers, so have no idea of the quality, but if I'd heard good things about it and had £69 burning a hole in my pocket and it was a special occassion? Maybe.