sweek wrote:

An Oyster is a little card that you touch in and touch out the gates
with. On buses, you only touch in. Get a PAYG one and you do not have
to worry about how much it costs. It will be the cheapest way for you
to get around. A trip will cost you 1 pound on the bus, and one fifty
on the tube. Put enough money on the card to make sure you can travel
around. You can check your balance at every station using the machine.

This is roughly the level it needs to be at, yes, though I think you
may be intending to be ironic. It needs to be put above the ticket
machines (or before you reach them) in tube stations to prevent the 4
quid rip-off occurring, and in several languages.

Next, you need to make it easier to obtain an Oyster by having it sold
from several machines pre-credited, rather than having to queue for
ages at the ticket office. (Note: many tourists will want to avoid the
ticket office as the language barrier may be an issue, let alone the
invariably long queue).

Neil