Originally Posted by
MSPeconomist
In these cases, the presence of partner flights which must be booked (if available at all) as low, forces additive pricing with respect to these segments.
The same issue appears in post #3 which uses an AS segment in each direction.
Not necessarily. I recently booked an HND-LAX-SEA with LAX-SEA on AS for 80K. The options for DL metal on both legs were 105K.
To answer OP's question - I've seen 400K+ one way for US-Australia in J, with 775,000+ round trip.