Originally Posted by
christep
Could this be because the ticket is issued on MU stock and this is the fee that CX charges for "revalidating " when making changes to tickets on other airlines' stock?
But that handling fee costs approx 40 USD.
HKG airport tax is charged for non-same day transit within 24-hours.
But, these charges can not explain 150 USD.
One possibility is the original fare permits only same day transit.
Some fare only permits same day transit. For that type of fare, if you want to make non-same day transit, a different fare will be applied.