Let's say that I want to fly the following 4 non-stop flights on different dates :

SJC-NRT (ANA/United)
NRT-SGN (ANA) 7:30pm
SGN-CDG (Vietnam Airlines)
CDG-SFO (United)

If I put them all in a single multi-city booking, it comes out to $4202 :

https://www.google.com/flights/#sear...tt=m;s=0,0,0,0

If I book them all as individual 1-ways (same dates), they come to :

SJC-NRT (ANA/United) $1073
NRT-SGN (ANA) 7:30pm $1022
SGN-CDG (Vietnam Airlines) $558
CDG-SFO (United) $3891

Ie. the total is even more, $6544 .

Now, by using hidden tickets and throwaway ticketing, I came up with the following combinations as 3 different bookings :
1) first booking : $692
SJC-NRT
NRT-SGN
SGN-SEA (throwaway this last one)

https://www.google.com/flights/#sear...GN0NH833;s=0,0

2) second booking :$558
SGN-CDG 1-way

https://www.google.com/flights/#sear...12-12;tt=o;s=0

3) third booking : $994
CDG-SFO round trip
Set the return date 8 months out - July 1.

https://www.google.com/flights/#sear...2017-07-01;s=0

Grand total : $2,244

Still not a great price IMO for coach tickets, but at least much more reasonable than $4200 or $6500+.

Questions :

1) why the rip off when combining all those flights on one booking ?
It's insane that you can safe 50% by adding 2 more flights. I could never actually fly the SGN-SEA . But I might very well keep and fly the SFO-CDG "return" ticket on July 10 .

2) It seems that when it comes to US-Europe flights, it never makes any sense to book a 1-way. So one can either have a throw-away return ticket; or always end with a spare "return" ticket for the next US-Europe trip...

3) are there travel agents or search engines that specialize in finding these types of tickets ? I have tried skiplagged.com, but it didn't work at all for these routes.

At this point, I think $2300 is still high for coach and November (not the expensive Xmas). The first stop (NRT above) is open, I would be fine going through another Asian city if it ended up cheaper. But SGN and CDG are musts.

Seems like one could possibly bring a discount Asian carrier into the mix (which won't show on google flights unfortunately) which would increase the # of bookings but could decrease costs greatly.

I haven't figured out what that might be. There are only a couple Asian destinations from SJC . NRT and PEK. A whole bunch more from SFO, though. From there, the prices to SGN are all over the place, can be $10 or $500 ...

If anyone has any idea, that would be greatly appreciated . I'm only looking to fly nonstop. And not looking to book with award travel. Probably will use Chase UR points at 1.5cpp for those booking. Discount carriers may not be possible through UR though.