How it works:
1.) I own a store. It sells stuff you normally wouldn't buy such as new pcs.
2.) You want a new pc and you've been looking around, but it's normally too expensive for you. (Lobster fishing no longer pays as much as it used to, unexpected expenses, etc)
3.) 50% off sale comes. OH MY GOD! WOW! Overhyping the sale.
4.) "Wow," you think, "now it's really cheap and I want it! Gotta buy it."
5.) I make money by selling stuff for a little less than I normally would and I get rid of inventory that I couldn't get rid of so I have plenty of room for my new merchandise in the next year. For example: new models of PCs or smartphones.
6.) Your wallet dies cuz it ran out of monies from all the "deals" you bought into. Reality: You cleared my inventory for me and made me some cash while you got something you want for less than normal.
TL;DR: CHEAP(ER) + WANT = BUY BUY BUY!
Psychology version:
Food used to have to be stored for winter otherwise you die. This instinct is still embedded in our mind. Today we don't worry much about day to day survival, but the instinct takes over with money (the perceived "survival" thing). We also associate new stuff with pleasure, something we are indoctrinated into since our early childhood. So retailers take advantage of these instincts and thus black friday is born. Deals + loss aversion + perceived savings = buying!
