the blackmagic is significantly cheaper than the c100 but you would also have to add equipment around it; thus making them similar in price once there both useable.
you could always consider an old red1 its a comparable price to both.
you can get a red one/mx for 5k - under 10k and it still outperforms a blackmagic. similar price and performance.
what would happen if you put a metabone speedbooster on lense specifically designed for micro 4/3