The MTBF is extremely low for this part; 2276 helos with 48 failed knobs a year. The critical factor would be time and complexity to repair. "Replacing a knob" is quite likely far more than loosing a setscrew and pulling a busticated one off and replacing it with a new and fashionably correct one and tightening it on the shaft. The failure is likely internal to a multilayer and tactile panel which is factory sealed and full of microminature parts which require a clean room for disassembly and to disconnect and reconnect the new switch (knob.)
I have taught troops such classes on these control heads back when MTBFs were less than 25 hours in the 1980s. Now, we have only 48 failures a year for 2276 installs - that is a MTBF of 1 failure (just coincidentally) of one failure per every 48 aircraft per year for this part.
To be honest; I got bigger fish to fry. If I was assigned this I would put a man full time to fix it, and if I had that man there is no doubt there are a thousand things more wasteful for him to fix quicker and easier.
At $50K a pop and 48 of these a year, that is $2.4M...you ought to look at what the USN pays a certain contractor for support services if you think this is a lot of money. The Army is VERY frugal.