My commute is only 10 miles per day so I reckon that I am saving about £35 a month in fuel (halved my normal monthly fuel costs). Unfortunately I can't get rid of the car completely as my family & I rely on this for other journeys when we need to travel together as a family. I will be saving around £350-£400 per year next year as I would have needed to purchase a works parking permit had I have still been driving to work.
However, a new Giant Defy on the works cyclescheme, cycle clothes, Garmin GPS, pannier rack, bags, pumps, tyres, inner tubes etc etc and I think I'll start actually seeing savings by around August 2018!! Especially when I've already got my eye on an N+1 for next year.
Saying that, the bike has been a positive lifestyle change (lost 3.5 stone in weight) and has given me a healthy hobby (don't have to pay for an overpriced gym membership that I'd no doubt get bored of a couple of months down the line) so whatever the cost, I try not to worry about the 'savings' too much.