Don't blame people for doing this, blame the idiots who buy them from these people.
If you allowed a person who would go off and buy 50 NES Mini's to just keep them then you have someone who is down $3,000 and has a massive pile of consoles which he doesn't want, but instead he will put them on ebay or in local adverts for $300, all it then takes is for 10 complete idiots to buy them at that price, to have it first in their collection over others, for that scalper to break even.
It is because of idiots funding these people that they exist, if the people who can't survive without a machine which can play a small collection of NES titles can't help themselves and must pay 5 times the retail value of the console to have it first... and then put it on a shelf and never use it, then they are the ones at fault here, I can't even begin to understand being upset at people for profiting from idiots.
If you ever pay over the RRP for a product which has been purchased solely for the purpose of both reselling it and purchased to buy up the available retail stock, then you are the cause of scalpers existing in the video game console area, and for that, I hate you, personally, just know that I think the people who do this have something wrong with them and are too stupid to even understand that they are the issue here.
Leave a scumbag buy up $3k or $10k worth of NES minis... leave him sit on them for months not buying them, then when the switch comes around that person won't be out buying up as many of those he can get his hands on to sell on again, like I said idiots fund these guys to do it, the money that they use to buy systems is normally handed to them from the last thing they sold at 6x its value.