The page FFF linked doesn't seem to indicate much of a problem. The prices compare well to any other Lycontinental part.
I have heard some very loud whinges along the lines of "those ***s at the CAA won't approve this silencer, they insist on evidence that it doesn't degrade my performance or a POH supplement changing the performance figures if it does, proof that it's not going to damage the aircraft, a JAR-form 1 and copies of design drawings - and ALL IN ENGLISH TOO when it came from Germany".
Or words to that effect. I'm far from the CAA's greatest fan but I suspect in the issue of approval of silencers they've been somewhat maligned unnecessarily.
But I do agree they're a good thing for GA in general if we can have them.
G