I had been interested in buying an Aeron chair for years, but always was reluctant to spend 700 dollars or so on a chair, because I am extremely cheap. Finally, one day when my back pain was getting really bad, I went to the Healthy Back store to buy an Aeron chair about 2 years ago. The salesman actually convinced me to buy a CXO chair for 800 dollars instead. I'm not sure if it's better or not, but it is pretty good.
It has made all the difference. It is rare that I get back pain now. Putting off buying a good chair probably ranks among one of the bigger mistakes of my life. A few years before I got my chair, I ruptured a disk in my back, and had to get surgery. Considering how great my back has been since I got this chair, I am convinced that if I had just bought myself a good chair earlier I never would have ruptured the disk.
The money I would have saved on surgery would have paid for the chair many times over....and who knows what saving myself a couple of months of excruciating pain and immobilization is worth. I literally couldn't get out of bed for most of the time that I waited for my surgery.
Oh and when I say a "good chair". I mean it. The chairs I was using before weren't extremely cheap chairs. They were always around a couple hundred dollars, which apparently wasn't enough to buy a chair that doesn't hurt my back.