[superuser2]

Bicycles cost ~50x less but can be rented at similar rates. Also it's relatively easy for a bike-sharing company to redistribute bicycles on a truck if the supply bunches up somewhere.

An hour of Divvy is surprisingly close in cost to an hour of ZipCar, which is astonishing considering how much more it must cost to operate ZipCar.

[akgerber]

Bikesharing is designed to encourage short trips within its service zone— even if you want a longer trip, you can just dock/undock a bike to avoid a fee (aka docksurfing). The escalating hourly fee is designed to keep the bikes in circulation, not as a charge you pay during ordinary usage— I've been a member of Citibike in NYC for over a year, and have never paid a fee beyond the membership.

With Zipcar, you first pay a membership nearly as expensive as bikesharing, then pay at least $10/hr.