First, as I've seen several versions of the OP's narrative in different forms on Facebook for a couple of years now; and second, since I find it hard to comprehend that an actual CHL instructor would devote class time to such a 'story' without mentioning situational awareness, evaluating a situation as it unfolds, or realistic alternatives to drawing a gun; I'm going to conlude that the OP's premise is complete & total BUNK.
But that's not to say that it doesn't have some merit. As CHL holders, the days of going about our mundane business in an almost mindless trance are over. Every situation, every encounter, every interaction has the potential to go south in a hurry. The difference is that now we've decided to take responsibility for our own & our loved ones' safety. So thinking about the scenario that the OP described is a useful mental excercise that will hopefully benefit someone in the future.
The first thing to think about is situational awareness. There's no reason that someone up to no good should be able to exit a vehicle, cross a convenience store parking lot, shout out a 'greeting', and get within arms reach of you if you are paying attention to your surroundings. Being aware of what's happening around you will give you the opportunity to evaluate the situation - is the person running toward you, hiding something in their hand, favoring one side as they approach. What's the tone of voice that the person is using? What's their manner - impaired, agitated, fearful. And even if there's no misgivings, there's no reason to allow someone to get within arms' reach of you. If I don't know a person, I don't have to trust that person & let them get close to me. The tone in my voice will let the person know that they'd better not come any closer. And any attempt to continue the approach will be met with a loud & forcefull "STOP!" My next action will depend on what they do...
And by the way. Do I think that a couple of bucks is worth someone's life? No, I do not. But in the OP's scenario, the bad guy has determined that a couple of bucks IS worth my life. And I will disagree to the best of my ability.
Opinions expressed are subject to change without notice.
NRA TSRA TFC CHL: 9/22/12, PSC Member: 10/2012