Instead of buying new pillows over and over, I just buy filler pillows (like these from Ikea) and removable covers.
Gracious Home (discovered on Etsy) has some of the cutest pillow covers that can be customized to match your decor. Check out some of my favorites...
The covers can come in four colors (white, natural, taupe, or black) and there are 35 print colors. Go give your couch/chair/bed a face lift!