[aetherson]

They're both basically hoping to increase their margins while still providing substantive savings to their passengers. So, for a $20 ride, they basically want to charge each passenger about $12 (thus saving the passenger $8) and thus increase their net take from $20 to $24.

The complicating factor is that they're also trying to provide passengers an incentive to try out the service before it gets good, so they offer some discounts even for rides that they think they will not actually be able to find an additional passenger for.

It's a very cool innovation. I hope it works out. It remains to be seen if passengers want to deal with sharing a car in enough quantity to make the services work out. If it does work out, then rides-for-hire will, in this sub-space at least, become a genuine network effect business, and there will be one hell of a brawl.