I saw it when I worked retail (which was a long time ago, so I guess as an anecdote, add an extra grain of salt; maybe things have changed but I doubt it).

We would get pallets of product right before Black Friday, and curiously, they would overlap with product we already had in the store. For example, if we carried a 40" TV from brand X (TVs are very notorious for this Black Friday swapping), we’d get a pallet of 40" TVs from brand X which looked exactly the same, had the same specs on the box, but a different SKU. In some cases we were instructed to remove the original stock and replace it with the Black Friday stock, which would be priced lower.

As others have mentioned, returns on the sale stock would be high. And there would be interesting differences, like an obviously cheaper remote or an overall lighter unit.

And of course sometimes there was no overlap – we’d get some product from some no name brand that just sat out in the aisle on its pallet. These were absolutely only brought in for Black Friday and I have to assume they were the cheapest imaginable garbage inside.

I’ve never sought out a Black Friday sale since those days.