I don't get it - how else would it be pronounced? To me it looks like the comparative of a hypothetical adjective "peeky" (compare "peakier"), or perhaps a form of a verb "to peeky" (compare "carrier"). Either way, the pronunciation seems to line up with theirs...

That's almost a plus: People in the know can feel smug pronouncing it the correct way, while the majority of people pronounce it the obvious way. See: Wikipedia's pronunciation.