"General everyday items fluctuating anywhere from $40 to $300," said Shoaff.
She discovered a growing new trend. Some retailers change 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.
Decide.com monitored prices of several items on a well-known shopping website. First, they tracked an iPad. At midnight the iPad was $511. At 6 a.m. it was $503. By 7 a.m. the price sunk to $475, where it remained until 2:30 p.m. and then jumped to $510. At 10 p.m. 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.
"The suppliers are constantly monitoring each other," said Buckingham.
Decide.com's tracking software found the price of colored pencils ranged from a high of $3.32 to $2.22 over a 24-hour period. In one day, the price for duct tape ranged from a high of $7.83 to a low of $2.00.
"What has changed fundamentally in the past 12 months is the speed and scale at which prices are being set," said Eric Best, CEO of Mercent Software.
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," said Best.
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 found on search engines, though.
"Free shipping, returns, make sure you're using those things to your advantage because sometimes just price isn't always the cheapest," she said.
What product's prices fluctuate the most? Decide.com says electronics, appliances, clothing, shoes, jewelry and even household staples, like dust pans. Some experts suggest if you ordered something from a retailer and the price dropped within a reasonable amount of time, contact the business and see if they'll refund you the difference.