Why do I always get significantly less crystals than anyone else?

Every time I finish a battle, it always shows that I've earned less crystals than others with the same or lower point totals, even if they're on the same team as me. I left an example below, where I had a higher K/D and point total than the person below me, and they still got significantly more crystals than me. He doesn't have a premium account and is also a lower rank than me. How is this fair?