Why are flights to DC so expensive?

We just moved here from the Washington, DC area, and in all of our research before and since moving flights back home to DC are more expensive (and inconvenient) than anywhere else we've seen. Kind of feels like we picked the worst place in the country to move for people who have 70% of all their friends and family in Virginia.

Flights are consistently $700+ per person for a round trip. I know obviously cross-country is expensive, but it's almost cheaper to visit our family in England than it is to go home. Visiting our friends in New Jersey can easily be only $300-$400 per person.

I guess complaining about it doesn't change anything but I am curious if there's a specific reason why, or if there's any chance it changes in the future. We love it here but don't want it to be so hard to visit home or have people come see us!