Amazon just had its best Prime Day yet--selling 175 million items to a "record" number of Prime members around the world. The bigger takeaway, at least for the independent sellers who take part in the discounting spree, is this: Prime Day is now a legitmate rival to Black Friday and Cyber Monday. 

The 4-year old shopping holiday, launched by Amazon to commemorate its 20th anniversary, has ballooned into a two-day shopping extravaganza, featuring deep discounts on everyting from Alexa-enabled devices to Yeti coolers. This year, Amazon's Prime Day results bested both its latest Black Friday and Cyber Monday tallies combined.

While it didn't divulge overall sales, the Seattle e-commerce giant noted that sales at third-party vendors--made up mostly by independent small- and medium-sized businesses--doubled over the period to $2 billion.

Beneficiaries included vendors like Sherri Yukel of the Menomonie, Wiscconsin-based party supplies company, Big Dot of Happiness. She says Big Dot's 2019 Prime Day sales ticked up more than 40 percent to $156,000 over last year's sales, which she adds is a bigger bump than she's expecting on Black Friday. "It's shocking to see such a huge spike in revenue year over year," says Yukel, whose company ran a 20 percent off promotion on some back-to-school items. 

Tahmi DeSchepper, owner of jewelry company, Tahmi, said she saw a nearly 200 percent increase in sales compared to this time last year, though she declined to cite specifics. Her Fairfield, Iowa-based company offered 30 percent off best-sellers for the pre-Prime Day sales, and 25 percent off select other items for the actual Prime Day. She added that the two days of Prime Day together were about half of her total sales on Black Friday. She suspects her products might have more appeal to year-end holiday shoppers than summer Prime shoppers.

"It's beginning to rival Black Friday for a lot of businesses, and as a brand, customers are starting to expect big deals on Prime Day, like they do on Black Friday," explains Carly Stein, CEO and founder of the Toronto-based wellness products company Beekeeper's Naturals. Her company participated in Prime Day sales with 20 percent off "lightning" deals. While she declined to provide specific revenue results, Stein reported an "incredible boost" in sales over the period since last year's Prime Day.

"We were expecting an amazing day but not as significant as a jump as we saw," she adds. "This is really the only the other time of the year where you need to accumulate inventory for such a massive one to two day spike."

Going Beyond Amazon

It doesn't matter how big your company is or whether you're even an Amazon vendor--retail calendars now revolve around Prime Day as much as they do around traditional holidays. Anand Siddiqui, a vice president of insights and analytics at the New York City-based search intelligence company Captify, notes that even major competitors to Amazon--Target, Best Buy, and Walmart--hosted their own sales around Prime Day. Target's push, for instance, noted that you don't need to be a member to score deals on its site.

"Amazon competitors are not only copying Amazon's massive 48 hours of hot deals, they are creating events of their own for consumers to look forward to. And it's working," says Siddiqui. He noted that all three companies saw spikes in online searches over the period. Best Buy, Target, and Walmart declined to provide sales results.

Now that the Prime Day sales are over, successful retailers need to figure out how to maintain the momentum until the next shopping holiday, says Stein. She noted that one of Beekeeper's Naturals products made its way to a No. 1 best-seller spot for cold and flu treatments on the site, where it still remains. "We expect the momentum from Prime Day to really drive the business in the latter half of the year and set us up for a huge Q4," she says.