Some of us might be drinking more than 6 pints (6 UK pints is about 7.2 US pints). That's one way.
Another way is paying more than $15 per drink, yes, after including tax and tip in the US. That's somewhat common in some places, especially if cocktails are involved. Or higher end wine or spirits. Or even certain craft beers.
I do live in an expensive area, but didn't mean to imply that the prices I'm describing are the lowest available. Some people choose to go to more expensive places, or order a more expensive option.
Certainly not here anyway, £5 already feels expensive so if it's that much I will probably only have 1. Can usually find places that sell you a £2-3 pint.
Norwegians complaining/bragging about high alcohol prices is basically a meme. But it's true that prices have shaped the way we treat going out and partying. BYOB is fully expected at private parties unless anything else is announced. People rarely head out to nightclubs without being properly boozed up from a preparty at someones home. A store bought 0.5L beer could be as low as $2-$3, while a beer at a bar or a club is expected to be ~$12 at a very minimum, but typically slightly above $15.