I may have written about them before, but I've had excellent experiences with J.C. Penney's Stafford oxford cloth button-down shirts. They're not the best in the world, but they're hard to beat for the price (currently $17).
Purists may turn their noses up at these shirts because they're a blend of 60% cotton with 40% polyester, as opposed to 100% cotton.
The other day, I came across two blue and white university striped OCBDs (neither in my size) hanging close to each other at a thrift store. One was a Polo Ralph Lauren 100% cotton; the other was a 60-40 Stafford. I felt them both, and guess what? You're probably thinking I'm going to report not feeling a difference, but it's more than that -- the Stafford felt softer.
Blends may be less than ideal, but they need not be deal-breakers. If it looks like cotton, feels like cotton, and the price is right, why not try it?