Buying airtime during Oscars telecast: $20 million. Having the most shared tweet: Priceless.

The fact that the Ellen DeGeneres' Oscars selfie is the most-retweeted tweet of all times is well known by now. DeGeneres famously used a Samsung Galaxy Note 3 in front of live-television for a selfie that captured some of the biggest names in Hollywood alongside her, names that included Brad Pitt, Meryl Streep, Kevin Spacey, and Jennifer Lawrence, amongst others.

Many have suggested that Oscars host DeGeneres was paid by Samsung for the little stunt that captured everyone's imagination (over 3 million retweets and 1.5 million favourites, at last count). Others pointed to the fact that DeGeneres uses an iPhone in real life (as evident from her subsequent tweets), so this was another case of a celebrity committing a faux pas as far as brand endorsements are concerned. Well, that's not entirely true.

The Wall Street Journal reports Samsung did sign a deal, but not with DeGeneres. Instead, it bought $20 million worth of airtime with ABC, the authorised broadcast partner of the Oscars in the US, and got itself a sweet-little product placement in the process.

While the stunt felt spontaneous, it wasn't entirely unplanned. As part of its sponsorship and ad pact for the Oscars with ABC, the TV network airing the show, Samsung and its media buying firm Starcom MediaVest negotiated to have its Galaxy smartphone integrated into the show, according to two people familiar with the matter.

Even in their wildest dreams, the Samsung executives who penned the deal won't have imagined that the tweet would go viral like it did, overtaking Obama's famous "four more years" tweet within minutes. At one point Samsung was getting about 900 mentions a minute on social media, according to Kontera, a company that tracks content on social media sites. Only 8 percent of the comments were negative, the company added, indicating that people had no complaints about the 'sponsored' nature of the tweet.

"It was a great plug for the Samsung brand," Allen Adamson, Managing Director at Landor Associates, a branding firm owned by WPP PLC, told WSJ. "Ellen's selfie is going to be more impactful than their commercials. You can't buy that magic of going viral."