A buzz and word of mouth spread is the lifeblood of an amazon business ... which is why they are willing to give away for free (or nearly free) some incredible and popular products! It is a perfect win-win. They win by getting valuable feedback and viral marketing on their amazon product listings ... and you win by getting free products that normally cost $20-$50 or more.
And by the way, there is no 'catch' at all. If you are an amazon PRIME member, even the shipping is free. At most you have to pay a little sales tax (unavoidable) and then start sharing on social media. That's it. You can see why this VIP BUZZ CLUB is so popular!