It’s about half price to book AU-HKG-PFT in PE one way than AU-HKG direct. Has anyone tried to throw away the ferry sector and exit through immigration rather than going into transit in HKG?

And i presume if you don't have any checked baggage in the first place, there shouldn’t be any issues?

Yes, not a problem to just exit immigration after landing at HKG if you don't have any checked bags.

Even if you do have checked bags, posts in older threads suggest the odds they let you check the bag to HKG only go up significantly if you have a long connection time (e.g. in the neighborhood of 7+ hours of more). Plenty of legitimate reasons why one would need it in my opinion (dropping items off for a friend/family that can't be transported in carry-on bag, need fresh set of clothes if you have an overnight connection, etc.)

What I would like to know too however is whether the best way to forfeit the last sector is to:
a.) simply exit immigration and no-show the final leg
b.) cancel on-line check-in after landing at HKG and then no-show the flight
c.) call CX and tell them you don't want to fly the final sector anymore.

I recently asked the same question in another thread and got a reply saying the "best" way is to fly the whole itinerary purchased but obviously it's not quite practical if your final destination is HKG. Also the terms and conditions suggest passengers pulling off this "skip-the-final-leg" stunt might be subject to a recharge but whether CX actually enforces this term is a different story based on several anecdotes I've seen on this forum.

I think you will find AU-HKG-MNL to be a significantly cheaper option than AU-HKG-Mainland China, especially in J. Book an overnight layover (most of the fares even have free stopovers) and you won't need to worry about anything, even if you have checked luggage.

Though i wonder if the repurcussion would be more likely / severe vs. the ferry given CX definitely operates the sector you throwaway

Airlines in general have massively cracked down on missing flight segments to do this. You might get away with it for the ferry, but I imagine they will plug that loophole before long if so.

aviation is the only business model i can think of where you paid for service/goods and not take delivery of, vendor has so much issue. Loopholes exist for a reason because of pricing logic flaw. I heard many of these "airlines come after you" urban myth but yet to see someone making a scene for getting reprimended for not taking a flight they paid for.

i wont argue arounds ethics or lack of, or pricing logic etc etc as i understand it and exploit them. but OP pls do let us know if you face issues. i would say if CX ever comes after, just say you got sick and your ticket isnt flexible so you chose not to fly.

I was not aware this was an option for getting to Guangzhou. I just tried a flight search for PFT on GF and a subsequent search on FT and did not find information.

How does one book a flight from NA to the PaZhou Ferry Terminal via HKG?

Personally I’d choose option d) check-in only for the first leg, tell the agent to send bags only to HKG which is the final destination.

This was what I did which I thought was the best for both the pax and the airline. As the pax has not checked in for the last leg, no-show fee appeared not a concern, let along the issue on bags. Meanwhile, it also helped save trouble for the airline, such as not having the need to look for the missing pax.

Only on CX website AFIAK

Did you do that in the app / at the airport? Did the agent not ask why you are not checking in the second sector that's on one ticket?

At the airport. The agent I encountered was familiar with the handling and did not ask any questions. YMMV though.