I find it interesting that people keep blaming the shops as though they're the only ones involved in this.
There's no shortage of people out there who, if given the option, will purchase armloads of rifles, magazines, and ammo at "normal" prices and then turn around to sell those at much higher prices to those who cannot find such things in stock but have a felt need to purchase them.
If that rifle, magazine, or ammo is going to be sold to the end user at a 50-100% premium over pre-panic prices, what's the difference if it's done by the shop or by some "unethical"* buyer?
Some people complain if the prices are raised, causing the buyer to reevaluate just how badly he or she "needs" the item. Some will also complain if limits are imposed on how many may be purchased at one time in order to allow as many people as possible to obtain the item ("Who is that guy to ration this stuff?").
I would contend that it is far from unethical for people to sell items at higher prices when demand has gone insane... it causes buyers to self-limit themselves at purchase time. Where they might have otherwise purchased many items, they cut back to what they see as actual necessity, allowing more to be available for others.
Moreover, it can also be that some people now selling things can finally get enough money for the items for it to be "worth" selling them... while they might have wanted to sell a firearm, the prices being offered were not high enough- $800 for a given firearm might have led to a "forget it, I'll keep it" attitude, but at $1300 the person might think "OK, now I'll move it out." In this way the supply can actually INCREASE due to high demand and high prices.
*(I use "unethical" in quotes there to not pass judgment, but to use the term as the OP did... referring to someone taking profit in a market gone crazy with demand, which is not necessarily unethical in an economic sense.)