Maybe, but they are buying them for exactly what they are worth at that moment in that location, and if they are willingly paying the asking price, then that is not insanity.....at least to them.
First of all, I haven't said, nor do I believe that the gun shop is doing anything illegal. The magazines belong to them and they can price them any way they want.
I think that you believe I am saying that the gun store is doing something criminal and that's causing you to defend their actions when no defense is really necessary.
With that out of the way:
1. Willing compliance with a demand is not evidence that the demand is reasonable or "sane". A person can comply willingly with an insane request or demand for a number of reasons.
Let's look at just one possible reason by examining the definition of the word "panic".
Panic: Sudden uncontrollable fear or anxiety, often
causing wildly unthinking behavior.
"Wildly unthinking behavior" is quite an apt description of "insanity".
2. The idea that "sanity" can be defined, one person at a time based on what the person in question feels is sane or insane (as you imply when you say "at least not to them"), is, to say the least, problematic. If the standard of sanity for a person is how that person feels about his own actions at the time in question, then no one is ever insane and no one ever does anything insane.
3. The idea that the mags are worth exactly what they're marked because panicked people are willing to pay the price is not really consistent with reality. During this same timeframe, I found one online retailer selling the identical item (which was in stock--at least for awhile) for $25 + shipping, and there were (and still are) several other local gun stores (within 10 minutes drive) selling the same items for less than half of the marked price at the particular local gun store in question. The people are paying $120 aren't paying that price because the mags are worth exactly what they're marked but because the people are panicked, because they don't know where else to get them and because they think if they don't get them instantly they might not ever have the chance again. None of those things makes the mags worth $120, it just means that the people buying them are not acting rationally, or do not have sufficient information to make a rational decision. In other words, insanity.