You should ask why is it available if you pay 50USD to 4pm. If it is not booked for someone else then it is available and then hence available for late checkout which is usually to 4pm. Poor implementation from the hotel. Some Accor hotels in Asia will even happily check me out at 9 or 10pm if I have a late night (early morning flight). I did not see that fairmonts are limited to 2pm late checkouts as well.