One major administrative cost is moving bikes around. People tend to take them downtown during the day, and out of the town at night. Even if you don't need docks, you still have to move bikes.
Bixi takes a lot of parking spots partly because finding space for large stations is difficult. By using existing bike racks, we can often put in bikes without modifying anything. Plus, although parking is lucrative, replacing room for one car with 10 bikes that 100 people can use is a good trade in our book.
The pricing incentives idea is awesome. A win for commuters, free marketing for your service, and free labor.
Someone would need an account for that, with payment info. Any plans to increase account uptake to serve that purpose?
We do take payment info on signup. Right now programs are localized so we set up different websites for each, but we hope to link everything together in the future. You can see an example at http://gt.viacycle.com