The financial benefit of cycling vs driving?

I was involved in a discussion on Facebook recently where it was suggested that cycling saves money. Now on the face of it, this would appear to be a fair comment. After all, when you're using pedal power instead of the car you save money on fuel...obviously! When you actually start to "do the math" however, it's perhaps not quite so clear cut. As a casual cyclist on my mountain bike during the summer, I was doing a couple of hundred miles a year at the most, I was wearing baggy shorts and an old football top, the bike would be

Now where did I put the pump...?

serviced occasionally, and so yes the odd journey to work was effectively free.  When however you start to take cycling more seriously, the cost savings don't always add up as you expect.  First of all, the more you use the bike, the more wear and tear you have to pay to sort out.  I had 2 flat tyres in 2013, and although they can be fixed with a repair kit, I ended up buying spare inner tubes anyway.  Then of course I got my hybrid road bike, which was through the government backed Cycle2Work scheme, but still costs me money from my wages each month.  With that bike came various accessories, a new stem to make the handlebars more comfy, a new bottle and holder, a new frame-mounted pump, and then as winter came I needed better lights, warmer clothing, that sort of thing.  Of course this stuff should in theory last me for a few years, and if I'm doing around 1800 miles a year on the bike and the cost of all the stuff I've already paid for, plus ongoing costs of a decent service each year, plus a bit more which may be needed over this time too for additional clothes, etc. is then stretched over say 5 years, then I reckon I'm looking at around £200 a year, which is just under 11p per mile.  That doesn't include the cost of the roof rack I bought recently either, at around £150, as it's not essential for the sort of cycling I'm talking about here, but that would put a bit extra on the costs.

However you travel it's not cheap!

At the moment our Auris Hybrid is costing around 12p per mile in petrol, and I'm expecting this to drop a bit when averaging out winter and summer, hopefully to around 11p as well, so I suppose really there is no obvious cost benefit to cycling.  You may of course say that I'm comparing the costs of just fuel against the cost of a bike and all the trimmings.  That's true, if I include the costs of the car loan, insurance, servicing, etc. then the car costs between about 31p per mile (based on 14000 miles a year) and 39p per mile (if that creeps down to around 10000 miles per year), much more expensive of course, but seeing as there are a certain amount of journeys which can only be done by car, then it's there anyway and from a purely financial point of view, it would be better to use that and not bother using a bike. In fact, the more miles done in the car the cheaper the cost per mile is, so by cycling instead of driving I'm actually increasing the per mile cost of the driving I do.
Savings and benefits though shouldn't just be measured in terms of money spent.  Cycling is fun & of course healthy, it's much more rewarding to the body and the soul than driving is.  For that reason, I'd say that everyone should really invest in a bike and reap the benefits.  If you don't drive at all then ditch some of your public transport journeys and get on your bike instead, you really will save money.  If however you've already got a car, then just get a bike anyway and reap the non-financial benefits instead.