If you’re one of the millions of people who will be boarding a plane in the coming week, you should probably know that you’ve paid an extra $20 for the privilege of going through airport hell over the holiday season.

The four biggest carriers levied a holiday air-travel surcharge  – labeled “miscellaneous surcharge” on your e-ticket receipt — of $10 each way on all domestic flights on December 19 and 26-27, and again on January 2-3, 1010. (Southwest is the only major airline that has elected not to impose the fee.)

It’s probably cold comfort that this practice has a lesson to teach in supply and demand. The Official Airline Guide estimates that available seats on domestic flights in November and December have dropped 3.3 percent this year, meaning competition for the seats that remain is stiffer over the heaviest travel months of the year.

As Newsweek reports, “A surcharge is a lazy way to make sure airlines rake in big bucks this year. It’s easier to slap a $10 surcharge onto every ticket than doing the complex calculations needed to raise prices by various amounts on thousands of routes ($8 more on one route, $18 on another, and so forth).” But flying surely beats driving if you live in Atlanta and your family’s in Boise.

If you’re up for a laugh, watch Louis C.K.’s comedy bit on how air travel is a miracle and yet nobody’s happy: