1. Adding the bag during checkout
The "+$250" offered at purchase is often not the price of a bag — it's a more expensive ticket that includes it. Take the base fare and add your bag separately, directly on the airline's site: often $50-75 instead of hundreds.
2. Paying for your bag at the airport
The counter is the most expensive place. Add your bag online in advance: most airlines charge much less before departure.
3. Ignoring the free personal item
Almost every fare includes a free personal item (backpack/handbag). Packed well, it's enough for a short trip and avoids any fee.
4. Not checking the total BEFORE paying
Some sites show a low price then stack fees (seat, bag, pre-checked options). Always check the final total and uncheck extras you didn't ask for.
5. Going over the weight limit
An overweight bag at the counter = steep fees. Weigh your bag at home and keep a margin.
FAQ
Is it cheaper to pay for a bag online or at the airport?
Online in advance, almost always. The counter is the most expensive option.
Is carry-on free?
The personal item almost always is; the cabin bag depends on the fare and airline.