I'm sure these are of good quality. But $21 plus shipping for these? There's about 5 cents worth of plastic here. I've been involved in plastics injection molding, so am familiar with how much it costs to produce items like these. And yes, I do realize the up front engineering NRE expenses. The only saving grace for you is that the price might not be totally up to you. Devilbiss may be raping all of their distributors in the same way. Your price was actually a little better than most of the others. I'd consider a fair price for these to be about $5 plus shipping for the whole set of 5 filters.

Good product.