Supposedly lyft’s cost per ride was $0.14:
https://mobile.twitter.com/mohapatrahemant/status/1102401615...
https://mobile.twitter.com/mohapatrahemant/status/1102401615...
All their AWS costs are probably not ride related, but most probably are, one way or another.
The marginal cost for one more ride, is probably much smaller, but I don't know that that is the right way to think about this.