Hotel prices can vary greatly depending on how far in advance you book, the demand for rooms, and which hotel you book but the prices below will give you a rough idea and you can do further research and hotel booking at
https://www.tripindicator.com/hotel.html
Ronald Reagan Washington NationalAirport Hotels:From $189 per night.
Baltimore/WashingtonAirport Hotels: From $119per night
Washington DullesAirport Hotels: From $199per night