Of course they're going to go with Samsung here. Samsung offered them more money. And of course Samsung offered them more money. James Bond films are gigantic in international markets. Samsung is number one in market share because of international markets. Of course they're going to stamp their brand on media that appeals heavily to international consumers.
Considering the dire financial straits this movie has already gone through in order to pay for its production, there's no doubt that they're going to go with the highest bidder. It's also important to remember that this product placement isn't just set dressing, it's an actual prop in the movie. So of course they're going to charge a lot for this.
Also, Samsung is actually offering a unique, top-tier product here, whereas there's nothing special about the Z4. It's just another spec upgrade of the Z3. Assuming this movie is as successful as Skyfall, you can count on Samsung selling a ton of S6 edges. Hell, it wouldn't surprise me if some of the establishing shots in the movie capitalize off of the Edge's features.