Here is how it works:

In YVR, I've worked in the past with ethnic agencies who used to get heavy discounts off the published fare. They would need this to be competitive in the market because, generally speaking, all airlines between YVR and a particular European country would be charging the same fare - unless you bought it from the airline or an agency upcountry that wasn't familiar with the ethnic market.

So, let's do an example. This has no relation to current pricing.

The peak season summer published fare YVR-IST is $2000.
The average selling price is $1325-1350.
The travel agency receives a contract from an airline like KL or LH offering a 37% commission on any sale that they make.
The price that the agency therefore must pay to the airline is:
$2000 - 37% [=740] = $1260 NET NET.
The agency adds a $75 commission so that the fare paid is $1335 + tax.
The ticket reads $2000 + tax.
The difference [$2000 - $1335 = $665] is documented by an MCO in that amount and is paid for out of relinquished commission.

In a busy market, that commission will shrink to normal levels as the airline is able to charge more according to supply and demand.

In early 1997, the CX published fare YVR-HKG was $2000 with the usual selling price about $800 lower. But for travel occurring in the month before and after handover of HKG from the UK to China, all discounts were cancelled and the full fare was charged. The planes flew full.