I agree with ¥ 0 ñ 9. Typically see 3-5x on lists with the occasional 1.5-2x at some wino-centric places. My limit for buying is typically ~2.5-3x based upon the situation. Anything higher than 3x for more expensive wines and I’m not ordering off the list.
I think +/- 3x is the norm in large cities on both coasts. As many of us know, and of course ironically, the good deals are often to be found at the higher ends, either because there a mark-up of 1.5-2x still yields big bucks, or because the restaurant bought it a while ago, marked it up, and not sold it, and in the meantime, it’s current price has increased. I wonder in your London place what the higher end looked like. I doubt that there were such exorbitant mark-ups at all levels.
in Italy it is usually 1.5 - 3 max vs. retail depending on restaurant. (median is under 2)
in uk I have usually found 4 - 5 x retail, but my experience is limited.