Checkout bots are nothing new. People have been using bots to snag stock on hard-to-get items for years now. There's been bid snipers on eBay, and all sorts of scripts that people run to purchase new-stock items on Amazon and other big-name retailers. Now those bots are being used to snag Switch stock before real people have a chance.
These Checkout bots are constantly tracking Switch shipments at websites like Amazon, GameStop, Best Buy, and so-on. As soon as inventory is updated, these bots swoop in and purchase as many as they can. Then those units go to resellers, and they flood the market with Switch stock that is ridiculously overpriced. Obviously the pricing isn't too ridiculous, as some people are willing to pay the premium just to get their hands on Switch.
Unfortunately, there are even Discord servers where these bot-users are showing off their Switch hauls, and talking about how much money they're making on each batch. The whole situation makes it much, much harder for those trying to buy a Switch legitimately. As of right now, anyone trying to purchase a Switch without paying insane reseller prices will have to go up against robots with perfect accuracy.