I don't doubt that cargo may not make a lot of money for an airline but removing it has more cost that removing luggage.
The cost of a lost Int'l bag is somewhere around $150/bag (including delivery fees, incidentals, customer perception damage, airlines extra handling (int'l bags require more work due to PPBM and customs)).
Cost of two LD3's of lost bags: 69 * 150 = $10,350
69 bags is roughly 2500lbs. It's rare for ALL cargo to fetch >$4/lb. Most cargo forwarders pay much lower rates.
In reality, the lead loading the flight has no idea what the cargo's worth. S/He has a list that prioritizes the pieces and then s/he looks at how many bag cans s/he should be getting and plans what to load where. Cargo gets loaded first, then the bags. Cutting cargo is common. I would say on the majority of our flights there were pieces cut. Cargo gets overbooked just like pax and not all of it has to be there overnight to satisfy the SLA.
Airlines demonstrate this day after day as they leave bags behind in favor of other things.
Except they don't. It probably happens on less than 1/10000 flights. I saw this happen twice in 7 years when I was around airport ops. Both times it was a mistake. 1) Rookie lead didn't follow the proper loading priority and thought he was doing the right thing by cutting bags. 2) AOG engine crane was a must fly to EZE to fix an INOP engine. It was heavy enough to cause an overweight scenario.
Whether the cost is delayed cargo compensation to the shipper, crew timeout, flight delay, or something else the cost is there and it outweighs the cost of removing luggage.
In some extreme cases yes, but it is extremely rare and certainly not the normal operating procedure. As I said before, the cost of 69 bags lost bags is far more than whatever the airline would have made for the cargo.