I just finished bringing my equipment log up to date after the protracted xmas-and-also-getting-ready-for-pbp session that has been the first two months of this year.
I've spent more on "wear" items in the last 8 weeks than in the life of the bike (since mid 2009) so the mileage figure has taken a beating - but I suppose this makes it more realistic, or at least, more worse-case.
The headline figure is: 3.5p per mile. That's what it costs to keep on the road.
The cost of ownership isn't so impressive - 33.2p per mile. All in, my 4 mile direct commute costs me £1.50 each way, even more expensive than getting the bus!
(And if I make it 27 miles by taking the extended loop, that's a cool £9.90)