Not to sound rude.. but $22 is not "a lot" for an air filter. Mind you you've got a Mercedes of all makes, albeit an old diesel, still the parts and maintanance items could become pricey. However, $22 for any make is not outrageous.. and "rip off" is definately what I wouldn't say it is. My friend recently bought an air filter for his late model Pontiac... and spent I think $45.

I would like to add more on this.. but I am afraid I would start a "flame war". So I will keep it at that.