Every time I've brought my Toyota Yaris in for it's regular service I was surprised to find a $50 charge for replacing the "cabin air" filter. It always annoyed me, but they assured me it was a pain to change the "special" filter.
Turns out that's bullshit. It's a cheap paper filter that takes about 30 seconds to replace. Corporations use proprietary parts and slip through overcharges for simple maintenance to add to their profit, of course. But this is an ultimately dis-honest practice that risks making otherwise satisfied customers, like me, angry and desirous of revenge for being duped.
Well here's my revenge Toyota, a step by step set of directions on how to turn a $5 household furnace filter into two Yaris cabin air filters. It took me an hour and a half to figure this out and make two filters and another half hour to write this page. Someone following these direction should be able to make a pair of filters in an hour, saving them (and denying you) $100!