MS and Sony pay AMD for design and then they fab them themselves. Amd doesn't make much money from consoles, especially when they didn't have much else going on and needed to win those to get some money in.  
Now years later with DX11 finally dying AMD can get some synergy out of having consoles on their platform and selling the same chips to consumers. Everybody is gonna optimize for Zen and Navi and low-level APIs like Dx12 is what AMD has designed their gpus for for years. 

The lows of 2-3s was caused by the horrible bulldozer and the fact that they hardly sold them, because they were terrible. Now with Zen they have the superior architecture, superior process, and superior yields. First time in history for all that, and it's gonna turn into a money making machine. Second half of 2019 is where the fun begins, and it doesn't end until Intel gets their process after 10nm going (10nm+ or 7nm) because current 10nm was designed as worse (for high performance) than 14+++ (which wasn't supposed to exist). Although it probably doesn't end there either because tsmc is killing it and doing 5nm risk production soon.

Tl;dr: consoles are low margin, but selling the same architecture to consumers and having it be the best architecture on the market will have great synergies.