You are making two important assumptions here:

1) Lower fares are distributed evenly across the L,V,Q and H.

2) All passengers are travelling point to point.

When a passenger buys a through fare, only a portion of that ticket revenue is attributable to each of the sectors flown. So the revenue attributable to a YYZ YVR passenger who originated in YHZ is less than the point-to-point fare in the same class. And even more so with the YYZ YVR passenger who is connecting to Asia, or the YVR YYZ passenger who is connecting to Europe.