[kelnos]

> I, the customer, am the one carrying the bag, there should be no reason to charge for it.

It's on the plane, so it takes up some of the limited storage space, and increases the weight of the plane, which means more fuel burned.

Saying you carry the bag so there's no reason to charge for it is like saying you carry yourself onto the plane, so there's no reason to charge you for the flight ticket.

So either they build the average per-passenger cost into the price of every ticket, or they charge a fee only for people who want to take on the extra bag.

[ftth_finland]

Airlines already use an average cost per passenger.

What you are looking for is charging passengers per weight.