system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it sometimes cheaper to fly to a city by buying a ticket to another city which uses that first city as a layover?

An example would be: I want to go to Denver.  I can fly to Denver for $800, or I can fly to Denver, then boulder for $700.  Only I never go to Boulder and I just ditch the airport at Denver.  Why would airlines charge me less to send an extra flight?
gpt
It used to be that airfare was just based on distance. They scrapped that a number of years back, and overall prices have come down, but the new algorithms are pretty complicated. They base prices on number of competitors going there, time to departure, seat inventories, demand expectations, whether it is a hub, weekend, weekday, time of the day, and other things. As a result, you sometime get the situation where it's cheaper the way you describe. on the downside, you can only get one way tickets that way and can't check baggage.