They constantly change prices
According to Woroch, online retailers use a tactic called "dynamic pricing" where they adjust prices based on consumer and market behavior to capture more customers.
"That means the price you saw on a microwave when you left for work in the morning could be completely different by the time you get home at night," she tells Business Insider.
Another way retailers can manipulate prices is by setting an "anchor price" on items to color a shopper's impression of every other price.
"Stores will make sure there’s something crazy expensive in the inventory to offset the expense of other prices," Ellwood tells Business Insider. "So everything else in comparison looks much cheaper."
The anchoring effect isn't limited to pricing. It's a cognitive bias also used in professional negotiations, where the first person to throw out a number has the advantage, because they provided the figure that will affect any others to follow.