Wow, that's expensive. They seem to be much cheaper here:
Some of them are obviously a bit more expensive but generally, they don't run to that much. So a 20% saving on some of these things would only be Ł20-30 - totally not worth getting into that scrum for.
I think the difference probably traces back to the differences between the typical US fridge and the typical UK fridge. For example, the typical refrigerator size in the USA tends to be much larger than that in Europe. I believe there's another current eHell thread discussing the differences. US "fridges" are also typically a refrigerator/freezer combination rather than just one or the other. The ones in your link appear to have no freezers, which would considerably reduce the complexity of the appliance. Finally, it's common for US fridges to have a dispenser for filtered water and ice on the front, i.e., on the outside of the door. This adds yet another layer of complexity and design challenge.
I use to work for the refrigerator engineering division of a major appliance company, and the quite expensive models I worked on actually had barely any profit margin. By my understanding, this is common for refrigerators (at least in the USA). They're complicated and expensive to make, so the price is already high enough to be a difficult sell to the consumer with just a small profit margin. The company's main profit came from the other appliances in the kitchen set, but the set wasn't complete (and thus not appealing as a high-end appliance collection) unless it included a matching refrigerator. The goal for the refrigerator division was basically to break even and be self-supporting as opposed to subsidized by the more-profitable appliance lines.
ETA: MommyPenguin mentioned $2000 for a nice refrigerator. The ones in the appliance line I worked on actually ranged from $2500-$4000. 20% off would definitely be nothing to sneeze at. Especially if the fridge wasn't the only appliance you were purchasing.
It's not the shopping for bargains; that makes good financial sense if it was something you needed anyway. It's the scrum. The frenzy to buy stuff purely *because* it's on sale. There are some really crazy videos on YouTube of 'Black Friday Montages' and half these people don't even look like they care or know what they're buying, as long as they're getting *something* that's on sale just because it's on sale. Just grabbing random boxes and going "yeah, I got something cheap!!!!" That's just ridiculous.
The other question off the back of this is: are there sales during other times of the year too, or is it limited to Black Friday? Here, retailers tend to have regular sales throughout the year in addition to the January sales (which is just to get rid of post-Xmas stock), so bargain shopping isn't limited to just one period.
Keep in mind that the USA is a big country with a lot of people. So for any nationwide event, there will be plenty of extreme behavior to make up some pretty crazy YouTube montages just due to the sheer numbers of participants, even if that behavior is a tiny fraction of what actually goes on. I personally avoid Black Friday, but I don't enjoy either shopping or crowds. I know other people who do enjoy Black Friday. I actually ended up getting taken along on a shopping trip on Black Friday a couple of years ago. We went in the afternoon, so no camping out. The store was very busy and somewhat crowded, but everyone was very polite and considerate. There were pretty substantial sales on a wide range of items, and a long line for the checkouts. Actually, there was quite a bit of friendly chatting and camaraderie among the customers waiting in the line for the cashiers. Certainly not a normal shopping day, but quite sane and well-organized. It's not my cup of tea, but I can see why it would be quite fun for someone who actually enjoys shopping. The folks I went with took a pretty organized-but-laid-back approach to the whole thing. They had a plan of various things they would like to find/check prices for and browsed a little for good deals on stuff that would be useful to them, but also had nothing they were determined to get.