But that's easy enough for retailers to work-around these days when they can ask suppliers for multiple UPCs for the same item
You can't do this for "bespoke" products which is where the UK law seems to most hit businesses - things like furniture which are specific to the retailer.
Of course the $1200 candy bar price is never the RRP :)
I took some pictures in Portland once of the most extraordinary version of this I had ever seen[1][2]. I thought they had taken it up as a high art, but a few months later, they genuinely went out of business.
Make sure to avoid the expensive store...
A product can be sold below this price, but not over it.
Restaurants get around this for something like mineral water by tacking on a "service charge" for opening the bottle and serving it to you in a glass.
An airport cafeteria tried to do the same but without the actual service - asked for Rs. 80 for a bottle with Rs. 20 price tag.
Some consumer went to court and the court fined the cafeteria some Rs. 10,000,000
(But you might get away with it, if it's outrageous enough to be clearly a joke.)