200 is not expensive, I had a pair of orthotics made for me for 400, but covered under my group health plan.
You should see a podiatrist first, then have the orthotics made just for you. There are orthotic shoes now, Nike, Reebok, Clark, Ecco, etc.
Actually everyone should use a pair of orthotics. They are amazing, your back problem, your sore feet and your knee problem could all go away in a matter of days witha good pair of orthotics. I use them all the time.