In fact, online retailers who sell common household items are also making adjustments throughout the day, especially for appliances and electronics.
If you buy an iPad in the Apple store, the price is probably the same today as it was yesterday. But on some websites that same iPad can be one price at midnight and a lower one at noon.
While shopping online recently, Amy Shoaff noticed prices for the same item, on the same website changed substantially throughout the day.
"General every day items fluctuating anywhere from $40 to $300," Shoaff said.
Some retailers are changing their online prices hour by hour, and sometimes even minute by minute. The goal is to have a product priced so it pops up as the lowest priced item in shopping search engines, or Amazon's coveted "Buy Box." That's where most consumers look to find the best deals.
"It's more a battle of getting the right screen position as opposed to trying to sell it as quickly as possible," said Chris Buckingham with the Professional Pricing Society.
Consumers can use the website Decide.com to monitor prices on shopping websites. It found an iPad at midnight cost $511. At 6am it was $503. By 7am the price sunk to $475, where it remained until 2:30pm and then jumped to $510. At 10pm the iPad increased to a high of $529. That's a total of a $54 price difference on the same site, all in one 24-hour period.
"What has changed fundamentally in the past 12 months is the speed and scale at which prices are being set," said Eric Best with software company Mercent.
Some retailers hire software companies, such as Mercent, to monitor the prices of its products and make changes based on its competitors.
"Because consumers now are researching their offline and online purchases in advance more than 50 percent of the time," Best said.
There are websites which will monitor prices for items you want and alert you when the price drops, or reaches an amount you'd be willing to pay.
If you add an item to your Amazon shopping cart and leave it there Amazon will notify you of price changes.
Shoaff has a warning about clicking on the least expensive deal.
"Free shipping, returns, make sure you're using those things to your advantage because sometimes just price isn't always the cheapest," she said.
The product's prices that fluctuate the most include electronics, appliances, clothing, shoes, jewelry and even household staples like dust pans.
What if you buy something, then see the price has dropped later? If the price dropped within a reasonable amount of time, contact the business and see if they'll refund you the difference.