999 and 9999 must be some sort of default input when the hotel made an error or forgot to change when entering their actual rates. Interesting that the other room types and rate types seem to be simply set as a supplement or discount to the main rate i.e £10 more or £50 more etc
This happens often when you are booking very far ahead. It will rectify itself eventually when the algorithm kicks in and sets a sensible price so just beware when booking that far out.