I _think_ you can get away with not selling ever at full price if your comparison price is the manufactures RRP.
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 :)
oh man ... furniture stores. The one down my street has been going out of business since the day it opened 20 years ago. Every few months they replace the "We've lost our lease!" sign when it gets too disheveled.
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.
But that's easy enough for retailers to work-around these days when they can ask suppliers for multiple UPCs for the same item