The trick used it to have a shop in the middle of nowhere (for example, north Scotland) which rotates products on the shop floor. This shop operates purely at a loss except for some desperate customers who will pay through the nose for a product due to convenience.
A mattress would be for sale at GBP 999 for 60 days there, and promoted as a discount at GBP 499 in _every other store_ they own. They make profit on selling 50x products at the discount vs. a single product at original price.
What is it with bedding companies and criminal miss representation of prices?
It's always SALE! SALE! SALE! Everything must go! %! %! %! or something similar.
The same was true for carpets for a time, but they seem to have fallen out of fashion, at least I don't see it that often anymore.
But this is a general thing in every downtown or shopping centre across all sectors. And similar for groceries. I enter all of these with one big default deny and fuck off mentality switched on.
What is illegal in many places is to increase the price for a very short period in order to then advertise an item as "on sale" with advertised discount based on inflated price, which is exactly what happened in the case you've linked to.
So advertising "was 739 now only 699" may be illegal, but listing at 739 the day before Black Friday then at 699 on Black Friday is not.