A fare that looks remarkably low frequently produces a trip that is not cheap at all. The mechanism is unbundling combined with the choice of airport and departure time.
The fare covers less than it appears to
The advertised price on a low-cost carrier typically buys a seat and a small personal item. A cabin bag, a checked bag, a chosen seat and any change to the booking are priced separately.
Each of those additions is optional in theory. In practice most travellers buy several, and the total converges toward what a bundled fare would have cost in the first place.
The pricing is deliberate rather than deceptive: it lets the airline sell genuinely cheaply to a passenger travelling with almost nothing, while charging more to everyone else.
Secondary airports move the cost onto the ground
Low fares are frequently attached to airports some distance from the city they are named after, where landing charges are lower and turnarounds are faster.
Reaching the centre from those airports takes a dedicated coach or a long train connection, and the transfer cost for a family can exceed the saving on the fare.
The time cost is larger still. Two hours each way on transfers is time removed from a short trip, and it cannot be bought back at any price.
Departure times create accommodation costs
The cheapest slots are early morning and late evening, because those are the departures most travellers refuse. That is precisely why they are cheap.
A flight leaving before public transport starts requires either a taxi or a night near the airport, and a very late arrival often requires the same at the other end.
Neither expense appears in the fare comparison, and both are usually discovered after the booking has been made and is no longer changeable without a fee.
Disruption is handled differently
A carrier operating a small number of routes with tightly scheduled aircraft has limited ability to rebook a stranded passenger onto its own network.
Where an airline holds no interline agreements, it cannot place a passenger on another carrier's flight, so recovery may mean waiting for the next available service days later.
Statutory entitlements still apply where the route qualifies, but the practical outcome depends heavily on how much spare capacity the airline actually has.
How to compare honestly
The only meaningful comparison prices the whole journey: fare, every bag that will actually travel, seat selection if it matters, ground transport at both ends and any night caused by the timing.
Done that way, low-cost carriers still win frequently, particularly for short trips with light luggage and convenient airports.
They lose reliably for family travel, long stays and itineraries where a missed connection would be expensive, which is the pattern the headline fare obscures.