

Is it the additional data you give them to enter the giveaway?
Basically. You’re telling TP-Link that you’re a business that’s interested in selling their products. In return, their Sales team now has your information and can pester you tell you all about the latest TP-Link products.
Additionally, they’re putting their products directly in the hands of customers who could become even bigger customers. If you, as a company, decide you like the product, then you’re probably going to buy more of said product.
Finally, TP-Link is being selective about who gets the freebie—they’re not just handing them out willy-nilly. From the fine print:
Offer valid only for SolutionX partners. One Insight S445 (2.8mm) camera per qualified SolutionX partner. Approval is required, and TP-Link reserves the right to verify applications
So there’s probably some sort of “legitimacy threshold” you have to clear in order to get the goodies.
One thing I’ve realized about Amazon, at least lately, is that they don’t always have the lowest prices. For many items, I can go directly to the manufacturer’s site and get the same product for a lower or equal price with free shipping. If I have to wait a couple extra days, so be it. At least I’m not lining Bezos’ pockets.