If you happen to follow a range of top-tier celebrities on Instagram and scrolled through your feed during the last week of January, you probably saw a number of them trying to smash a massive candy heart with a wooden mallet. It wasn’t immediately obvious what the heart was made out of or why it read “Bae,” “Ride or Die” or “BFF,” but the casing eventually gave way to a small box with a new Valentine’s Day fragrance from one of Kim Kardashian’s eponymous brands, KKW Fragrance. Upon opening their gifts, some celebrities discovered that the heart was made of chocolate and took a bite.

Over the past year, we’ve spent a significant amount of time analyzing the explosion of celebrity brands, with a big focus on the unrivaled direct-to-consumer growth of Kylie Cosmetics. With that amount of social capital, one of the biggest benefits of launching your own brand is the ability to tap into tens or hundreds of millions of followers on social media. The power of this reach is clear: Kylie Cosmetics has earned hundreds of millions of dollars of annual sales without any major advertising. In our Q4 2018 Megapone Report, our new quarterly benchmark analyzing the digital marketing strategies of 44 digitally-native and traditional consumer brands and retailers, Kylie Cosmetics didn’t run a single paid advertisement on Facebook or Instagram, a decision that stands out during the busiest shopping season of the year when brands are thirsty for sales.

But there’s a benefit beyond a celebrity brand founder’s distribution channel: The Boomerang Influencer Effect, or the second-degree proliferation of the brand on social media.

KKW Fragrance, for example, specifically timed its gifting campaign so that referential social media posts would be concentrated around the launch date of its Valentine’s Day products. In the span of a week, Kylie Jenner (124 million followers), Khloe Kardashian (85 million followers), Kourtney Kardashian (72 million followers), Kris Jenner (24 million followers), Chrissy Teigen (22 million followers), Paris Hilton (10 million followers), Ashley Graham (8 million followers), Busy Phillips (1.5 million followers) and many other celebrities and influencers posted their own videos smashing the chocolate heart and propelling KKW Fragrance into the feeds of at least an additional 346.5 million followers, on top of Kim’s 125 million. Strikingly, 305 million of these accounts (88%) come from people following members of the Kardashian family. While there is definitely overlap among fans who follow the entire family, not to mention drop off (not everyone who follows these celebrities sees everything they post), the reach of KKW Fragrance is still unparalleled.

And yet the cost of this reach was nearly nothing—even if the 150 or so heart boxes themselves cost $500 each with shipping ($75,000 in total), reaching 346.5 million eyeballs amounted to only about two-thousandths of a penny per viewer, which might be the cheapest CAC in history. (Even if only 25% of these viewers actually saw one of the posts, the cost is still negligible. This doesn’t tell us how many people bought these products or are planning to in the future, but it’s likely that with a limited inventory run and this massive reach, they have been selling quite well.

Beyond that, many potential shoppers are quite annoyed that the actual product doesn’t come with the chocolate heart and mallet to smash it, evidence that the stunt—and the boomerang—possibly worked too well.