Some (online ) sellers use algorithms to predict what they shall offer you next. There are some ways in which we can beat the system (using options after predicting how such predictors work). In principle, use a website to track prices, the smart buyer can play day-trader with such data and wait for a favorable time to buy. It's unbelievable how volatile prices can be.
This are more specific tricks:
- Say, you buy special wines and you think the retailer who had the best price last year will have it again this year. But some online retailers with dynamic pricing have better offers to new customers than to repeat buyers. So, let the system think you are a new customer (block cookies and website data in your browser, or better use a cookie-disabled browser ...
- When making an online purchase, put your wanted wines into the virtual shopping cart and click "checkout". Provide your name and e-mail address, move on to purchase info, but dot enter your credit card details. You may get an e-mail with a special offer
There is much more in William Poundstone's book: Rock Breaks Scissors: A Practical Guide to Outguessing and Outwitting Almost Everybody.
People are predictable even when they try not to be. William Poundstone demonstrates how to turn this fact to personal advantage in scores of everyday situations, from playing the lottery to buying a home.BTW, I have especially enjoyed Poundstone's book: Labyrinths of Reason: Paradoxes, Puzzles, and the Frailty to Knowledge
Another real option from the blogosphere: innovators use trial installations of special online shop technologies to test markets and promotion