Wonderful run down on the bike sharing situation in China. In regards to the notion that 1 RMB per half hour is cheap, I would say it is fair. One RMB has buying power equal to about one USD in most situations.
I've lived in different cities in China and US. 4-6 RMB to 1 USD in major cities like Beijing/Shanghai, and 1-3 RMB to 1 USD in less developed cities or sururban area. Less developed a city is, less RMB to USD in purchasing power for most domestic goods.
In the USA if I need a quick breakfast I grab a bagel with a spread for about $3; in China I will grab a noodle bowl for 3 RMB or a couple baozi for 2 RMB each.
Other points I use to come up with my recommendation that outside Beijing and Shanghai you treat 1 USD to be equal to 1 to 2 RMB.
Bus Ride - $2, RMB 1-3
Quick lunch - $8-15, RMB 10-20
Beer at a basic bar - $6-8, RMB 8-12
Beer at store: $1-2, RMB 2-4
Of course this is for domestic products in both countries. Imports cost more and follow exchange rate. For example, in China imports are usually exchange price + 25% import tax (electronics, cars).