If you want a cheap flight from Exeter to Washington DC, you've got zero airlines to choose from.
You can use the filters on your search to see more flights and find cheaper rates – Washington DC has more than one airport. So if you don't need to fly into Washington DC Ronald Reagan Washington National Airport, it's worth checking your other options.
If you're planning on going to Washington DC during this time, you could take a look at other airport options. Or you could try to get a last-minute bargain.