You can use Southwest out of BWI to BUF and rent a car. I see rt fares of about $125. AC has special rights into DCA and they have to pay for RCMP on every flight - so it's expensive. I don't know if "WAS" includes IAD but I did get a reasonable deal on UAL for YYZ-IAD. And of course there are all those interesting routings via ORD or DTW.