I have a 1968 260B and back in 1995 I had the Wholey Cowl put on by LoPresti.
(Wholey Cowl: an aftermarket streamlined cowl designed to increase cruise speed. )
When the Wholey Cowl is installed, the air filter is changed from the standard one to a round one made of black foam in the shape of a cylinder. This filter must be changed every year and (according to LoPresti) the filter can ONLY be bought from LoPresti.
A few years ago I took my plane for its annual inspection and the shop said "you need to get this filter - we don't stock it." I called LoPresti and found that they wanted $45 for this little filter (which looks like a humidifier filter, a cylinder shape about 5 inches in diameter and 6 inches long)!
Thinking I was being smart, I had them send me three of them for $185, and supplied one to my mechanic at each annual for three years. Little did I know, I should have ordered several dozen!
This year when I went to take the plane to the mechanic, I found I had used up my three filters, so I called LoPresti to order three more. Curt LoPresti informed me (with a straight face, or so it sounded over the phone) that the price is now $185 PER FILTER.
I'm writing to ask my fellow Wholey Cowl owners if any of you have an alternate source for these things?
I am so disgusted at the idea of paying that much for that little, that after a long silence and having him repeat the price a few times, I just hung up.
I'm reminded me of a problem the Lake Amphibian Owners Club had around fifteen years ago, when the manufacturer (who had long ago stopped making airplanes) realized that he was the only person in the world who anyone was allowed to buy Lake landing gear trunions from. Since a broken one grounds the airplane, he decided to change his price on that part from $600 to $6000. Because he could.