The three regimes
Budget: everything unbundled — bags, carry-ons, seat selection. The fare is a seat; the bag is a product. Legacy domestic: first bag $30–40, second $40–55, thirds steep — the post-2008 unbundling standard. Full-service international: one or two bags included, because long-haul competition still competes on inclusion.
The booking-time decisions
The fee class is visible at booking: basic economy often strips the included bag; status and airline credit cards restore it. Ten minutes of fare-class reading before purchase routinely saves $60–120 per person per round trip — the highest-hourly-rate research in travel.
The redistribution playbook
Fees are per-person, not per-family: five bags across four people beats three bags with thirds. Heavy packers redistribute to light packers before the airport, not at it. The counter is where fees are paid by the unprepared; the group chat is where they are avoided.