Spending money on a good chair is totally worth it. I picked up an Aeron back in 2006 and it is still going strong today. I think I paid around $700 for it, so that breaks down to $100 a year. I know up front costs like that are hard to do all at once but if you can buy quality items such as a good chair and desk and keep them for a long time it totally pays off. I did this with my desk too. The Fit System from Anthro is bad ass, aside from having to move it.
Seconded. When I started my business I was sitting on a pretty ordinary Staples cheap-o office chair. Within a year I felt like I was eighty years old -- my back was killing me, especially when standing up or sitting down. It felt like how it must feel to be Grandpa Simpson.
I eventually bit the bullet and bought a better chair (a Steelcase Leap -- see http://thewirecutter.com/reviews/best-office-chair-is-the-st...) for around $850. Man, it hurt to spend that much money on a freaking chair. It felt like ridiculous extravagance. But it wasn't long before my back pains were completely gone.
If you make programming your profession, you're going to be spending most of your life in two pieces of furniture: your bed and your desk chair. There's lots of places where it's OK to cheap out, but don't cheap out on those.
http://www.sit4life.com/products/Herman-miller/Aeronreg-chai...
http://www.anthro.com/getdoc/406c4518-c3e1-4447-8e77-bfd5944...