I pay £36.80 a week for unlimited travel through zones 1-4 on London Transport (specifically the Tube, Buses, Docklands Light Railway etc).
After the bullshit I've had to go through this evening to get home, however, I do wonder why.
I heard the Circle line wasn't pleasant, at the very least!
I don't use public transport often. Generally my use is limited to a very occasional Oxford-London day return. I'm always too lazy to book in advance, and buy at the station when I get there instead, so the cost is astoundingly high. Something like £40 for a peak day return for what, a 120 mile round trip? Off peak is around £20 I think. (those prices are totally from memory, so may be off by a bit, and have probably gone up anyway).