Using big meetings like CES is a cost-efficient way for Amazon to meet face-to-face with many of these sellers at once to tell them about new programs, as opposed to having a dedicated sellers' meeting or trying to meet them individually. CES, the world's largest consumer electronics event, is particularly popular with many Amazon sellers because it gives a peek into the latest gizmos and technology trends. It's also a great place to meet other brands and distributors within a short period of time, sellers say. Amazon conducts similar meetings at other events, sellers say.

Amazon's marketplace now accounts for over half of Amazon's e-commerce volume, and has grown rapidly in recent years by giving millions of outside merchants access to Amazon's global fulfillment center, logistics system and shipping relationships as well as its huge customer base. The company now has more than 5 million third-party sellers, according to FeedbackExpress .

The meetings are part of Amazon's effort to engage directly with its third-party sellers and help improve their overall selling experience on its site, as the company continues to deal with complicated problems such as allegedly unfair suspensions and stamping out counterfeit products .

While Amazon is once again putting Alexa front and center at this year's CES, behind the scenes the company is busy meeting Amazon Marketplace sellers to promote a new support service that costs between $30,000 and $60,000 a year.

Will Land, CEO of Marketplace Valet, a company that consults and sells for other brands on Amazon, is one of the sellers that Amazon invited to meet with them at CES, to discuss a seller support program introduced last year, the Marketplace Growth program. The service gives sellers access to a dedicated Amazon manager who provides hands-on support, including personalized coaching and training, as well as guidance on fixing issues that may arise in Amazon's marketplace. It comes in three tiers that cost between $2,500 and $5,000 a month.

In a room called One Amazon at the Venetian, Land was able to meet Amazon representatives and ask how exactly the $5,000 tier would benefit his business.

Although the program launched last year, Land wasn't aware of it until he received the invite last month. He says the 30-minute meeting helped him better understand the program.

"Anytime Amazon invites us for a meeting, we attend," Land told CNBC. "Getting a direct, consistent contact at Amazon is gold for any seller, so we're excited about the opportunity."

This isn't the first time Amazon held meetings with sellers at CES. For instance, Land met Amazon's advertising team at a previous CES to learn about their newest ad products.

Sellers also say Amazon likes to meet them in person at other trade shows or conferences to hold "speed dates" to discuss their new services.

Judah Bergman, an Amazon seller, said he once met Amazon representatives at the ABC Kids Expo, a trade show for baby and child products. At the event, Amazon representatives gave updates on its hazardous materials policy and explained how it would affect sales for certain toy products. He said he also met people from Amazon Business, its marketplace for business customers, at a different trade show in the past.

"These meetings help educate sellers of the business benefits they can be partaking in," Bergman said.

It's a particularly effective strategy as it reduces overhead costs to organize the meetings and makes it easy to establish a more direct relationship with sellers in one place, according to Abe Chomali, the founder of XP Strategy, a marketplace consulting agency. Doing so can build trust and gain confidence of sellers who may be skeptical of new programs.

"It's a great way to make face-to-face connections with many sellers at once," Chomali said.

Andrew Arnott, CEO of SellerSEO.com, a consultant for Amazon sellers, says he didn't take the meeting with Amazon at CES because he's not sure the program would be worth the fees of $2,500 to $5,000 a month. Other sellers expressed similar concerns in Amazon's Seller Forum about the company's general seller support system, while some said they were not aware of the Marketplace Growth program at all.

"It's probably more useful for very large brands who need a more hands-on approach and can handle the high fees," Arnott said.

Still, to some sellers, the increased face time at CES seems to be working in Amazon's favor. Land, of Marketplace Valet, said the meeting was good enough to convince him to buy in.

"Amazon said they had a lot of kinks to work out [last year] and revised the program," Land said. "We're signing up for sure."

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