Checked-bag fees can add major costs to your trip. But many travelers often fail to realize that cheaper, “low-cost” airlines often have checked-bag fees as high or higher than the major carriers. Spirit Airlines, known for its super-low fares, charges those outside its “fare club” $30 to $100 per checked bag depending on how the tickets are booked. When the average price to check your first bag is $25, that’s not such a stellar deal. And be careful with some budget airlines abroad: On easyJet, you’ll pay about $18 to $34 if you register your checked bag online. But make the mistake of waiting till the airport, and the price will be anywhere from about $50 (at the bag drop area) to about $70 (at the gate). In short, checked-bag fees can really get you down you if you don’t plan ahead. Of course, there are exceptions: Southwest is a winner in the baggage department, where both the first AND second checked bags fly free. And JetBlue — which only recently started charging for checked bags — costs $20 if you check in online or at a kiosk. Want to know how much your next trip will really cost, all fees considered? Check out Business Insider’s guide by clicking here.