Decided to go for CX255, entered credit card information then when confirming HKID details it timed out. Re-ran the search and the price changed (from 4110) to 15310! Closed down all browser windows and repeated but the same. Tried IE (was using Firefox) but the same. Rang CX and after a long wait she told me that their system was updating prices and she would have to make the booking for me. The final price was slightly up HKD6707 to HKD7127.