Unless you want to wait in a very long line, it is worth spending the extra $$ to skip the line. The audio guide was very informative. You may want to bring ear buds, they are not provided and you have you hold the device to your ear.
A thought provoking experience, remembering that these skulls & bones once had lives, hopes, troubles be they good people or bad. Audio guide was good to have & one could take time to take it all in.
This experience only has a few reviews, but you can read what other travellers have to say about the operator.