Ok, I reckon I should address this question sooner rather than later. I often answer, “it can be, or it can be cheaper.” But really, what I want to say, is it depends on how you look at it.
If you look at individual products, then the eco option can appear more expensive (although not always!). Of course it also depends on your budget and what you are used to paying for things.
Often its a case of comparing up front costs to lifecycle costs. Studies of newly built eco homes in the US show that while the upfront costs tend to be slightly higher, these are quickly offset by the lower operational costs. Low energy lightbulbs also cost more upfront but the save you money in the end.
Another way to look at it is the indirect costs that come from non-eco products… what if they increase your health care bill down the road, or cause loss of work? Or increase the overall cost of healthcare in society? For most products the price doesn’t reflect the full cost to the environment of the product. Including these costs can make eco products very competitive, although that subjective process can be tricky.
So my thinking is that knowing a product minimizes damage or even benefits the planet does have some value, and usually it’s worth paying for.
Photo by Clip Art (really!).

I think this is a very sensible way of looking at things. Often, we are ‘penny wise and pound foolish’ and look at things from a short term point of view. With awareness on the rise and resources dwindling, it is the duty of each and every one of us to be globally responsible.
I recently faced this question when my top-loading, water-wasting washing machine died. Do I replace it with the same, for a few hundred dollars, or upgrade to a front-loading, high efficiency machine for two to three times that much! I decided to upgrade, and am thrilled with my choice. Our first water bill showed an almost 50% reduction in water use, and because the machine spins so much more water out, our drying time is cut by two-thirds, saving gas and electricity. The machine will pay for itself financially in a few years, and I feel better knowing I have done the environmentally responsible thing.