You may remember in the initial PEY rollout, CX was quite aggressive but in the end removed a row of PEY from the A330s, and then removed PEY from some otherwise long haul configured aircraft. These also fly to India. But many passengers from India fly on to USA and not other places in Asia. So I'm not sure this bolded sentence is the reason why there isn't PEY to Dubai - it just seems like that market doesn't work.
Although you raise a good point, I'm not sure that disproves it! "the market doesn't work" is certainly a less explanatory narrative...because the lack of PEY alone says that! The parlor-room debate is
"why" doesn't it work? My pitch is that DXB has a higher % of short-haul transit than other places. I don't know for sure but I suspect it's on the right track.
What's more, about half the India flights now
do have PEY (with 77W). DEL and BOM now get at least one PEY-equipped 77W a day on most days, and MAA gets 77W a bit more than half the time too now!
So then the question would be...why didn't CX put one of the 77K rotations on DXB? DXB, especially CX731 / 738 has a very similar rotation pattern to the India flights served by 77K. Why is India getting those birds instead of DXB? (From my understanding, virtually the entire 77K fleet is accounted for in rotations. It's one-in-one-out at this stage). I think the answer is: India has more connecting long-haul traffic and thus PEY pax than DXB does.