I would also argue that there is some grey-area here. Part of that occurs in the amount an "investor" purchases.
I was lucky to get two UPCs. I've opened one, the other I'm keeping sealed, completely covered in bubble wrap, and placed in a cool dry spot in my house with 0 sunlight. Am I a scalper for purchasing more than one even though I don't plan on selling this product for over 10 years? I'm sure there are some people who would consider me one.
But what about if I cleared western Canada's stock of UPCs? And what if I still only planned on selling them after 10+ years? Is that still investing? I'd argue that it's scalping at that point. Or at the very least, just being really scummy.
Scalping -- buying up lots of stock immediately, creating artificial scarcity, and selling for a profit quickly -- is bad because it ONLY hurts people that would have otherwise gotten the product normally. You're taking a product that was going to be sold to a person for retail, buying up all the supply, and then reselling that product to that same person for a premium. The scalper did not have to exist for this person to acquire the product. You're being a middleman when there was no need or requirement or necessity.
As the other anon mentioned, the "investor" at least needs to exist to a degree because there would be no way to get a sealed box of an item that's out of production for 20 years otherwise. If you want to open a 1st ed Base set box, you need someone that kept it sealed for 20+ years.
But where do you draw the line on time and amount?