I've not read all the papers, so I don't know if all of them have the ad. The one I saw was in The Guardian.
I'd say it was a bit more than a misprint, as artwork had been prepared, presumably checked, checked again and signed off.
It almost certainly should have read 'from £199', as this is the online fare after the £10 discount.
I see that AA are offering LON-NYC fares at £187, presumably the same base fare with less expensive add-ons.