A set of pillows with inserts will run about $200 for a 2003 Optima. If they are original, they will need replacing. A set should last 3-4 years. If there is no ozone or if the ozonator is not working, I personally would just eliminate it. If you feel you really want to replace an ozonator, I would purchase the Sundance models as they work with the icons on the topside controller where another manufacturer's may not.
I am not sure if the 03 Optima still used the rotating jets or if they have the bearingless jets. The therapy seat will definitely have them but the other seats may not. Both are fine, but the bearingless jets will most likely never have to be replaced. If the jets are the rotating type, they swap out in a second and are easy and inexpensive to replace.