> Unfortunately, the business logic underlying much of this personalization remains a mystery.<p>Price discrimination appears, at first glance, to be about maximising profit, but really it's about <i>clearing the market</i>.<p>Say you're a cinema, and you set your list price for a ticket at £10. 20 adults show up and buy the tickets and are happy. Then 10 students show up, scoff, and go home - they weren't willing to go above £7. The market has not cleared: you'd be happier with £70 from them than the nothing you've got, and the students would be happier being £70 worse off but having seen the film. Neither party got what they wanted, no trade occurred, and no economic value was created.<p>The situation could be improved so that everybody gets what they want without harming anybody else: set a student rate at £7. Students get to see the films and your cinema makes more money - everyone is as happy as they <i>could</i> be.<p>In this example, the criteria for price discrimination is discovered by intuition, existing knowledge of students, maybe surveys. But even this isn't ideal - what about that one <i>really</i> tight student who buys pasta in 20kg bags and who values a trip to the cinema at £4? Ideally you want their £4 and they want to see the film - but how to cater for them without shooting yourself in the foot by making the student price £4 across the board?<p>Until the advent of the internet and fancy algorithms that could at least try to understand you, you couldn't. But today maybe we can.<p>Everyone has their own "true" valuation for a given product (<i>not</i> how much they think it should be worth, but how much they're willing to pay), and if you're a supplier with a magic ball which can divine this with 100% accuracy then you're as well selling your product at 1p over cost if that's your customer's true valuation. Again: they get the product they wanted and you get profit you couldn't have had any other way, and everyone's as happy as they can be.<p>But we don't have magic balls, and you can't ask someone for their true valuation because suddenly you'll find yourself knee-deep in a bartering game of bullshit and lies. Your only option is to try to divine it somehow.<p>This is what these guys are doing. And it's a good thing. To say "this is wrong and it should stop" is incredibly selfish - with reference to the example above, an equivalent statement might be "Yes I'll pay £10 to see this movie, but only if those students don't get a discount, which I implicitly understand to mean robbing you, dear cinema owner, of £70, and those students of the chance to see this hot new flick, even though both of those things are fuck all to do with me."<p>If you're a habitual bargain hunter (not out of necessity, more as a personality trait) and you're feeling affronted by this then all you need do is take a cue from these companies and adjust your tactics to suit the 21st century. Googling around may have done you proud up til now, but the world has moved on. I daresay that once you've mastered the art of using a VPN, user agent spoofing, and possibly the cultivation of a set of dishonest consumer profiles, you may find you'll save <i>even</i> more money in the face of this new enemy.