YSK that this is indeed illegal in many places such as the EU for example.

However those tricky manufacturers have a few tricks to get around this. One of the things they do is to create special "discount" SKUs. Despite their name, these SKUs are often not discounted at all and kept artificially high. Their specs usually aren't great, so the value for money is poor most of the time. However when something like a holiday sale comes around, these SKUs get discounted massively. That way the shops can still claim the discount is huge and would technically be legal, even though there are plenty of other very similar SKUs in the same series that were available for less.

This isn't a new thing, so called "retail" SKUs have also been around for a long time. Ever since webshops started out-competing retail stores manufacturers have been creating retail SKUs. These are often very similar or the same as another SKU in the series, but given a unique number and sometimes name. These SKUs are then only sold by distributors to retail outlets. Then when a shopper is in the store and looks up the price of the SKU on the internet, they don't see a dozen webshops with a lower price, but instead only other retail chains with a very similar price. This is to stop people from going to stores, get advice and look at all the models, only to then buy the selected model online. Of course smarter people can easily figure out which SKU is the corresponding non retail SKU. But if you are smart enough to do that you can probably figure out what model to buy without going to a store.

Still it's good for the law to exist and it does help a lot. The whole SKU shenanigans are only for some things, such as TVs, notebooks, appliances such as washing machines and vacuum cleaners, and some other stuff people usually go to stores to buy. For a lot of smaller stuff, such as PC components for example, this usually doesn't happen.