Airbox mods are not uncommon for Ducatis. Ducati people seem to delight in spending money.
I have heard from several sources that velocity stacks are a great upgrade for HyperMotards, and really do make a difference there.
My personal inclination is not to change much, and not to fix things that aren't broken, so I'm still running the stock setup for my M900.
1993 Ducati M900 Monster "Patina" (265,000 miles, killed by minivan 30Oct17) -- 1995 Ducati M900 (wife's bike) -- 1979 Vespa P200 (daughter's scoot) -- 1964 Vespa GS160 (160cc 2-stroke) -- 1962 Maicoletta scooter (275cc 2-stroke) -- 1960 Heinkel Tourist 103A1 scooter "Elroy" (175cc 4-stroke)