Simon, that’s probably the most constructive. At the moment here we have airlines competing to fill seats. AirNZ used to give 30kg, up from 22kg, with sporting goods. (Bike) Recently they stopped that and the 22kg check in now applies and there is a $30 bike handling fee. When making a booking recently and checking the sporting goods policy as soon as they gave me the policy change I cancelled the booking. (nulled their heavy advertising) Other airlines here became more attractive and have good service. Don’t know whether it upset them, but it saved me money. And yes, transiting through with the same airline they check it through with $30 handling charge at each transit. Starts to add up. As in the next trip to Canada it would be $180 (New, I live in our capital city but it only has a short haul international airport so I have hours of transit just to leave the country to most places)
And definitely, at airports a little ingenuity makes life easier. Even essential.
New, it does make life easier if you aren’t stuck with needing a box. Many places I go to you simply wouldn’t get one. To just ride to the airport and wrap the bike makes life easy, and saves money. More so if a trip includes several flight. Don’t know what your sister paid, apart from the inconvenience and cost of her two trips from the shop, but most shops offer packing service. One here charged $30, a few years ago, may be more now. Even at Bris they charged $20 for a box, pack your own bike, and their boxes are heavier , excess weight charges, than a bike shop one. Starts to make a bike bag a cheap option (and convenient, most are small and light enough to carry ). Again the plastic sheet I picked up in China for a few cents and carried on many trips was cheaper, but not the same protection. Of course there are many bags available at varying prices. Some even have wheels. Some are hard cases that convert to a trailer, no panniers needed.
Whatever.