Ask most people what to look for when booking a flight and they'll say the price, and the price is the one number that tells you the least about the trip. Two fares can match to the dollar and still be nothing alike. One lands you at 9am with a short connection in a single terminal. The other lands at 1am after a five-hour layover in a city you didn't plan to visit. Same cost, same route on paper. Two very different days.
The sticker price is a real signal. It just isn't the whole itinerary, and the parts it leaves out are the parts you actually live through.
The three things the price hides
Arrival hour is the first one. Landing at 9am and landing at 1am are not the same purchase, even at the same fare. An early arrival gives you the day. A late one costs you the evening and often the next morning too, because you're checking into a hotel at 2am and sleeping until noon. Read the arrival time before you read anything else.
Layover placement is the second. A 90-minute connection in one terminal is fine. A 45-minute one where you change terminals and clear a gate on the far end is a coin flip, and if you lose it, the "savings" turn into a missed flight. This is the same math as what a layover is actually worth: the hours count, and so does the risk.
Time zones are the third, and the sneakiest. A red-eye that crosses three zones can show a short flight time and still eat a full calendar day. The clock on the booking page doesn't warn you. You have to do the subtraction yourself, the same way you'd count the lost day on a red-eye before calling it cheap.
What we do about it
We won't rank a flight higher just because its number is lower. When the three fares we send each morning land in your inbox, the arrival time and the layout of any connection sit right next to the price, so the trade is visible instead of buried. The cheapest fare and the best trip are sometimes the same booking. When they aren't, you should be the one who gets to tell the difference.