Hm, often AirBnB is the only way "poor" people can afford traveling and a cheaper accommodation. Who does not say hotels have a secret cartel agreement?
I think AirBnB is a good idea as long as one shares the accommodation with the owner.
Nevertheless, AirBnB in DC was more expensive than a hotel and I did not like my host in DC.
But I will definitely write to AirBnB for the DCC fee in case this will happen.
Thanks for pointing out other options like homeaway.