Problem solved!!! It turned that the reason I thought we were robbed is that the rental was for over one month so we only received a partial payment. I was unaware of this as we hadn’t had rentals over a month long before. When the remaining payment came through a few days ago it was clear that the exchange rate was in line with a reasonable rate ie circa 1.38 usd/£. surprising that the Airbnb help desk didn’t spot this and make me aware of it.