I tot up the train fare I've saved - today I went through the £350 mark (I travel by bike every day I'm in the office but am only there 50% or so of the time).
What have I spent that £350 on?
New chainset, new bottom bracket (+ labour for servicing), new rear wheel, SPD pedals and shoes, new tyres (slicks and knobblies to replace the X-country tyres)....
2nd bike, 2nd computer, duplicate lights and (presta valve) pump........... (and more SPD pedals)
Inner tubes, bottle cages, chafe ease, savlon, plasters and dressings...
But, when I started commuting by bike a few years ago, it also made me start taking my own pieces in. The money I've saved from not using sandwich shops is pure HUGE!! and I guess some of the wear and tear could be blamed on my not-commuting cycling too.