Most of the best DIY products have multiple uses. I don’t know about WD40 though but vaseline has been working fine for a long time. only reason to spend 80$ on lubricant is if you over 30 joysticks or something. ortherwise you would be better off buying new switches,shafts and springs.
Vaseline is good stuff.
I have had the same thing on a few (new) sticks I have bought in the past, both of them stopped squeaking after a period of time. One of them was a JLF by the way, the other was a LS-32-01.
Vaseline? are you kidding me? Wait till summer comes. you’re found out what will happen. 
Err what’s going to happen. It’s going to heat up and blow up the joystick?
use qunk plumbers silicon grease at lows. stuff is the shit. stuff is 5 bucks