wrote to uk.transport.london on Fri, 10 Sep 2004:

After a trip to Paris recently, it occured to me that it would be a
good idea for the tube to offer cheap single tickets in Zone 1, along
the lines of the Paris system (maybe £1 for a single in Z1, £7 for
10).

The do, although not that cheap. You can buy "carnets" of 10 tickets
for something like £15.
--
"Mrs Redboots"
http://www.amsmyth.demon.co.uk/