A bit hard to tell. Its quite likely that the HID bulb is
faulty. You could try switching over the passenger side HID bulb to
the driver side. If the flickering don't occur, then chances are
your ballast is safe.
HID bulb is not exp to replace. Ballast is a killer.
Original toyota ballast about 700sgd, depending on where you buy it
from. Its only one ballast, not two.