Earlier quoted context omitted.
It's not income directly for him, it's paid to his label, and that label will take their own cut. My impression is that the label takes the largest cut of all the people involved, but I'm happy to be corrected on that.
Not to forget that Weird Al is doing a lot of covers - so he is not the original composer of the song. Performers usually get paid way less (everybody can perform a cover of any song out there), but the composers get paid the lion share. I also doubt he gets $12 but probably lot more, the video is just intended to draw attention to Spotify's payout schemes.
In terms of creativity, artistic vision, lyrical difficulty or any other metric, Weird Al should be understood as an incredibly talented musician.