If you ride enough that you can actually get rid of a car, then you can save money pretty fast. We still have two cars in my family and even though one sits in the garage on most days, I still have to insure it and keep the licenses up to date. Also, if you work or live in a place where you'd have to pay for parking, using a bike instead can be a huge cost saver.

For me cycling is as much hobby as it is transportation and as such I tend to spend some money on it, though not as much in the last couple of years as I did previously. I've got all the winter clothing I need already and although there's about $200 worth of improvements I'd like to make to my road bike, I've held off this year. I'll probably spend another $300 or so yet this Fall on a new gear hub, wheel, and disc brake for my winter bike. I'll sell my old Nexus Red band wheel w/roller brake for about $200 hopefully.

Anyway, I don't think I'm saving huge sums of money by riding and maybe not anything really. Our cars do have low miles and I suppose that saves us money over time because we won't have to replace them as often but modern vehicles can last quite a long time if you take care of them.