Why do people buy more than one item and sell it for 300% of the price?
Sometimes it is life, sometimes they make a living and other times it is because demand exceeds their want.
For the first one, I preordered multiple LoZ special editions because I wanted one. You can say what you will about this, but I am sure anyone who had their Master Edition Amazon order cancelled today probably wishes they had, assuming they hadn't done so already. Another is that I preordered a Switch, did the GameStop trade in and had to preorder a second. So, because of life I have two switches and multiple special editions. Now I could do the "good" thing and cancel the extras, but it's hard to do when I don't know if any of them will pan out (see Amazon example) and even harder when I am not in a financial situation where I can say no to $50 to $100+ easy bucks.
Making a living goes without saying and the last one is pretty obvious. Some people might love the Master Edition and got a preorder, but I'm sure several people would rethink their desire for it if they could sell it and make enough to basically pay for the cost and a Switch. I mean, the sword is cool, but sometimes the lure of $300+ in profit far exceeds your desire for something like that.
They buy them for 70$ and sell them for 100$ (300%...not, but you know what I mean).
If you've ever tried to sell anything, you would be surprised how hard it is to sell it at a fair price. My go to example is the Wii U. People will buy it for $200 with multiple games and accessories, but even with seven more games, two more controllers and other things, I couldn't get a single CL person to bite on paying 1:1 with GameStop.
The opposite also holds true. When someone underprices something, you typically don't see people agreeing to pay more. Sometimes it happens, especially if the price is really good, but most times people will GLADLY rip you off if given the chance. The same is true here. If I could make $260 in profit, why would I trade that for $30? I get being a nice person or trying to help a fan, but anyone is a fan when they can turn around and make $230 profit off your blunder and sometimes fans piss me off.
Best example I can give is when I put up my CL ad for my other Zelda special edition, I got someone who offered me a whole $2.50 for it. Their explanation was a long winded poor as me story ending with their love of Zelda. All I saw was an insulting offer. I mean, even if I want to be a good person, at $2.50 it would be better to just cancel the thing and hope for the best.