The NY Times had a feature on folding bikes today. I bought one about 8 years ago, a Dahon that cost me about $400. It was the perfect bike for me because I was living in a tiny (cheap) studio apartment where I had limited storage space. I wish I could say I was cutting down on my commuting costs and quitting my gym because I was riding the bike to work, but for me, it's a bit too long of a haul to ride all those miles and go over the Brooklyn Bridge... or perhaps I should say I am too wimpy to ride all those miles and go over the Brooklyn Bridge. And I'd have to keep my gym membership anyway, so I could take a shower before work-- there goes one part of my savings!
Nevertheless, a folding bike is a great option for people who commute in urban areas, especially if you need to use public transportation for part of your trip-- many of these bikes can be stowed in the overhead rack on a train. Even if you don't fold them, they are smaller than other bikes and will annoy other passengers less if you're going to bring them on the subway. All the more reason I am a wimp. But if I still kept buying Metrocards for the subway, there goes the rest of my savings.
Not all these bikes are as cheap as the Dahons. The Brompton pictured above will set you back almost $1,200, but I think you get what you pay for-- from what I've seen, these have a much easier folding mechanism than the bike I have. And since I've just determined that I can't actually save any money by riding a folding bike to work, I'm even less willing to invest in quality!
Oh well-- I will probably continue to let my bike gather dust in the basement in between my occasional recreational rides. But don't let that stop YOU from becoming a frugal, fit and fabulous bike-folder!