It's always interesting to me that so many people seem to completely lose all compunction about stealing once technology is involved. If they were ordering from a cashier at McDonald's and the cashier got distracted for a minute and somehow forgot to charge them before finishing the order, most of the people that abuse a bug like this would tell them about the mistake. I've been in similar situations plenty of times,…
This is the same anti-empathetic "what can we get away with" dynamic as stores engaging in surveillance-based advertising, deploying menacing robots that bother customers, setting up mobile device tracking and facial recognition cameras, price discriminating with coupons and routine sales, etc. Also when any customer service fleshbot says they "can't" do something because the computer says no.
It's only as technologists that we see the details of technology as ultimately mediating interpersonal actions rather than just taking its presence as a given. We know better than to mess around with holes in apps this way, largely because it's in the category of malicious hacking which generally gets punished pretty hard (burn the witch!), especially if you are one of the first to find such tricks.
But I personally am not going to get too upset over some individuals getting occasional freebies, especially while similar abuse by businesses tends to get normalized and then scaled up.