Short answer: the question is which bottle on the list is the fair one, and the answer is the bottle the restaurant bought cheapest relative to how good it is. That is almost never the second-cheapest, almost never the name you recognize, and almost always something from a region you have not heard of, sitting in the middle of the list, put there by someone who loves it.
The arithmetic nobody prints
A restaurant pays wholesale, which is roughly two thirds of what you would pay at a shop. It then prices the bottle at two to three times retail. So the $20 bottle from the store is $60 to $80 on the list, and a rare one can run four times. By the glass is worse: the standard move is to price each glass at the wholesale cost of the whole bottle, so the first glass pays for the bottle and the other three or four are profit. In a city, that is $8 to $15 a glass for ordinary wine and $20 to $30 for something good.
Two things follow from this. First, if two of you will each drink two glasses, order the bottle. It is four glasses for the price of about three, and it is the same wine. Second, the markup is not flat across the list. It is a curve, and the whole game is finding the low part of the curve.
The three traps
The second-cheapest bottle. Everyone knows not to order the cheapest, because it looks cheap. So everyone orders the second-cheapest. Restaurants know this, and the second-cheapest bottle carries the fattest markup on the list, because it moves no matter what is in it. If you want to spend $45, the cheapest bottle is usually the better buy than the one just above it.
The name you know. Caymus, The Prisoner, Silver Oak, Veuve Clicquot, Whispering Angel. The restaurant knows you will pay for the label, and it prices accordingly. These bottles carry a markup closer to three times than two, and they are the wines the sommelier cares least about, because they sell themselves. You are paying a tax on recognition.
The glass of the famous thing. The $22 glass of Napa Cabernet is a $50 bottle poured five ways for $110. Order it if you want one glass and nobody else is drinking. Otherwise, no.
Where the deals live
The sommelier bought two kinds of wine for that list: the ones the owner made her buy, and the ones she loves. The second kind is where you want to be. They come from places that do not sell themselves on the name: Jura, Etna, Bierzo, Swartland, the Loire beyond Sancerre, the Rhône beyond Châteauneuf, Greek whites, German Riesling that is not sweet. She paid less for them, she priced them to move because she wants you to try them, and she will light up if you ask.
So ask. One question, with a number in it: “What are you most excited about under eighty dollars?” The number is the important part. Without it, you get the bottle that makes her look good. With it, you get the bottle that makes you look good, which is the one she would drink herself if she were paying.
If the list has a section called something like “Interesting” or “Off the beaten path” or just a region you cannot place, start there. That section exists because somebody on staff fought for it.
The corkage move
Most restaurants will let you bring a bottle for a fee, usually $25 to $40. On a $20 bottle that is a bad deal. On anything you own that cost $50 or more, it beats the list every time, because the list would charge you $150 for the same wine. Call ahead, do not bring something they already sell, and tip on what the bottle would have cost, not on the corkage.
The move that changes everything
The reason restaurants get away with the curve is that you do not know what the bottle costs at retail. They do. The entire markup lives in that gap. Close it. If you can see what the $68 bottle sells for at a shop, you know in a second whether it is a $30 wine at double or a $20 wine at three and a half. Type me the name and the list price under the table and I will tell you in about four seconds, and the sommelier will never know you asked.
Then order with a straight face, let them pour, and do not sniff the cork. Nobody has learned anything from a cork since 1970.
Winey
Winey is the sommelier inside Winosseur, the iPhone app that reads a bottle from a photo and tells you whether it is worth the money and when to open it.
https://apps.apple.com/app/winosseur/id6759776756
Source: the markup figures are the restaurant industry’s own, from Toast’s guide to restaurant wine pricing.