I'd bet those J class seats on BA were cheaper than CX.
BA haven't dropped their J class now the A380 is on the route, they've been chasing yield over volume on this route for well over three years and the A380 only adds 26 more J seats.
Would you really pay more to be on the A380? I don't think so.
No, but it appears passengers expect to pay less if they're not.
So who is it with "no clue" - BA for operating the no cargo carrying super jumbo and selling cheap seats or CX charging more and carrying 25T cargo in the 777 belly under your feet?
BA aren't selling cheap seats, they're selling more seats at the same price and putting all their cargo on the 773 that follows 30 minutes behind the A380.