This appeared on the Going Underground blog:

http://farm3.static.flickr.com/2341/...65864844f3.jpg

As the Circle line runs exclusively in Zone 1, I suppose I shouldn't
have been too surprised about the result. The least expensive stop on
the Circle Line is Aldgate, with average property values hovering
around £396,000.

The Victoria Line came as the next most expensive line to buy property
on, with average prices reaching £1,109,107. Green Park was most
expensive stop for property on the Victoria Line with average house
prices above £2 million. The least expensive stop was Tottenham Hale.

"We were somewhat surprised to find the District Line appear in the
seventh position, given it includes areas such as Fulham, Richmond and
Wimbledon and follows the Circle Line through many parts of Central
London. It would be interesting to see where the East London Line
would rank today if the 2010 extension was already in place." said
Michael O'Flynn, from FindaProperty. Apparently the Essex parts of the
District Line weakened its overall average.

The Waterloo & City Line came in at last place as there are "minimal
residential pockets" around Waterloo and Bank stations.