Just did a 2 minute video for a small division of a large company and ONE track was going to cost us $3500. some independents charge that much to score an entire film! i won't be using this service anymore. the music is good, but its much more cost effective to hire a pro to cater to my needs at that price point... and they'll do it much cheaper.
The built in NDs and super clean xlrs that you get from the c100 will far outweigh the low noise and 60p that the a7s has for documentary filmmaking. I have both and love what the a7s can do but I've shot 3 feature docs now and all were shot primarily on the c100.
$19000. seems pricy but you really can't beat it in PL especially if you have a 16:9 sensor and don't want to loose pixels on the side. Alexa classic owners are rejoicing everywhere. i'm on their waiting list.