The history of Black Friday is quite interesting, has its origins back to a time when it was nothing to do with retail sales.
What frustrates me about these things is the way they start to be used and abused by retailers. Black Friday becomes something like 'Black Friday event!' and instead of being a day extends across a weekend, week or more! No doubt there'll soon be 'Black Friday month.'
Whether it's this 'sale' event or any other, the way I look at buying is as followings. Do I need the item? If yes, is the ticket price acceptable to me? If yes, I buy it. I take little notice of 'was £x, you're saving £y' and all that guff. There was an interesting documentary on x years back about retail pricing, 'sale' events and so on.
Btw I'm not saying there aren't bargains to be had.