I don't know everything, I do try to analyze a situation to see what the intent is in situations. I know places where it's a used store and most comics, if not all, are cover price or at most $2.99-3.99. That's just the way they price them, and every once in a while you'll see something like Bane breaking Batmans back at $5.99, while Howard the Duck #1 1st gwenpool is still $2.99-3.99. I'm not sure tye relevance in price distribution here or the ends and outs, I just trust they have a process. Some they seem to price more generously than others.
That said I don't feel a sense of duty per se, but I do understand others willingness to allow for corrections. I'm not so much hitting the garage sales and or antiquities with any kind of regular desirable books to know what "I'd do for their lack of effort"; although I do know my impulse on places I've found stuff is to talk to management to find out how they acquire and price or OTHER!
In my case the stores of antiquities or other are known for giving pennies on the dollar when these type come in, and are passing those cheap costs onto any potential buyer. Those places often have the comics in a random box in the corner. One place at least has a bin, another has them bagged and boarded, which I think is old dealer stock that they've acquired to keep the bins fresh or in rotation. Most places it seems would rather have a person come in for comics and wind up buying other stuff or becoming a regular as well. Not many care about "comics" as opposed to regular books, which has long been the case.
Comic con and LCS are different, but deals and steals aren't usually the case, one more than the other. I would say most of us have a relationship with our LCS to be friendly for future deals though.