Yes, after taking a closer look, I do see the difference in the YQ, but I still don't understand why?
If it's based on the region, then it should be the same because the two OW segments fly the identical route that the RT does.
YVR - LHR YQ - $433.00
LHR - YVR YQ - $293.11
YVR - LHR - YVR YQ $866.00
DIFFERENCE = $139.89