It's hard to do that in a physical store since everyone can see the same price display. I doubt many people would be happy in a store where they need to look up every single price on their mobile device.
Kohl's seems to be doing pretty well with that system. They print a high price on the tags, then discount it by rack, and mail out 30% off coupons with short expiration dates to some of their rewards card holders every month.
> I wish there was a mention that 5 people can buy the same milk and all can each pay a different price (and none know what the other paid either)
And the answer why it isn't mentioned in the article is... because it's not a thing that's happening.