Factor in the down time? Repair costs?
So Monetary loss or possible monetary loss = The right to kill
Preventing wasting your time fixing something = Mow them down with an AR
Sorta kinda not really. If they are running around smashing your store up, lethal force can be justified because you cannot know if they're going to just stop with property and instead turn on you or loved ones when they're done. A group of six young males jumping around in your store with tire irons, pipes, etc breaking everything for the simple sake of breaking things is really hard to predict.
It's because of the uncertainty and high stakes of these situations that make them so dangerous. Retreating is good in theory but makes several assumptions.
1) That you had sufficient warning of the impending SHTF situation, which was the case in New Orleans when the majority of people left before Katrina hit. The LA riots however struck with very little warning.
2) That you have secured a means of escape. Cars were some of first items destroyed during the riots. Roads can be blocked or destroyed faster then most people realize. Driving out of the riots for instance you'd be more likely to kill someone by running them over as you tried to get out. Assuming they didn't jump on your hood and smash your windshield out.
3) That you've secured a refuge, which is probably the easiest of the three points to plan for and the least likely to fail.
The situation those guys were illustrating in the videos was not just a pissed off minority group. Those were the LA riots. 53 fatalities, $1 billion in property damage, lasted almost 6 days before the situation was under control. Biggest kicker being that the police were ordered to withdraw at the
start of the riots for their own safety.
In the end it took about 4,000 soldiers from the national guard, the regular army and the USMC to restore order. Worst of it was over by day 4 but the troops weren't effective until day three when they rolled in. 72 hours is a long time to wait, especially when emergency services were unable to evacuate many of the wounded.
Also, understand that a rifle can potentially be just as effectively without having fired a single shot. Pointing the rifle at the mob and shouting, "Get the f**k out or I'll shoot you!" can be just as effective at stopping an angry mob-o-loot-rape-kill as shooting them all.
If they move on, hey it's for the best. You don't waste bullets, the store stays intact, most damage done is to a bunch of egos. This is what happens most the time in those situations.
If they choose to attack, then they do so at their own peril rather then yours. Still a considerably better alternative then thinking happy thoughts and hoping they won't hurt you.