I don't think it should be illegal, but morally it's at best a grey area. But, that's part of what's supposed to be a free market. You see an opportunity to jack up your prices 50% to take advantage of people in hard times, well people are probably going to remember that in 6 months when you're not the only place to buy something anymore.
There's a burger place here that's awesome and pretty reasonable for prices. Went to a music festival a few years ago and they had their food truck out there. Prices were double what they normally charge, no surprise there. But then when the festival is closing they keep selling food they know they're out of and refuse to give anyone refunds. I've never patronized them since. Yeah, they made an extra $10 off me once, but they lost all my future business for it too.
Then don't buy it if you don't like the price. How much money went into development, marketing, logistics, regulatory compliance, etc? It may seem like that layered cardboard only costs a few cents to make, and from a pure material cost it may be, but that doesn't mean the real world cost is anywhere near that.