I disagree with you that scalpers are not unethical. They are providing a service which people are willingly paying for. There is noting unethical buying something and reselling it for max profit.
Well, let's scenario this:
First, let's start with ethical/unethical. When I say unethical, I'm saying, "I don't think your actions are morally upright, but there is nothing illegal with it, and do what is good in your own eyes, you live your life, I live mine.
Take drugs. I think that taking hard drugs is unethical. It leads to broken lives, and hurts not just you, but often those you love, and even uninvolved people(say, pedestrians as you drive).
That said, while I think it is unethical to take hard drugs, I think it's your own choice, and should be legal. Until you harm someone else, like car wreck as an example.
So, that out of the way, three scenarios:
1.) Retailer of ammunition. See's supply chain all messed up. Knows that shortages will last a year or more, and that if there is no ammo, people won't but guns, accessories, or rent range time. And that this will likely depress the market even when the crunch is over. Raise prices to keep in business? Sure, that's an ethical choice.
2.) A private individual, who bought 1000 rounds of 9mm three years ago, at $0.20/round. Wants to sell ammo, see's prices for ammo is now, let's say, $0.80/round. Knows that if he sells it lower, someone will probably just flip it to that level anyway. Is it ethical to sell at the current market rate? I would say yes.
3.) A private individual conspires with, lets say, 8 other people, to buy up all the local supply of ammo at a lower price in a large store, and circumvent purchase limits designed to allow more people to buy the ammo they desire. Then, creating a local shortage in the area through their actions, or continuing the current shortage, they sell this ammo at greatly increased prices. Is this unethical? I would say yes. Do I think they should be allowed to do it? Yes.
Would it have been unethical for one person to buy in a store, then resell? No, they waited there, and got it, that is ethical. But working with others to induce a shortage(whether they thought about it or not), and circumvent purchase restrictions? Yes, that's unethical.