The whole situation is confusing as hell. I am using i3 + Polybar on a XPS 15 9560 laptop 4k display. Naturally, HiDPI is a nightmare of mine so I "fixed" it by appending following lines to the
/etc/profile
file

export GDK_SCALE=2
export GDK_DPI_SCALE=0.5

However, I also use papirus icons that seem to be recognized everywhere except for polybar tray.

Whats even more interesting is that if I remove my modifications to profile, the correct papirus wifi tray icon is used by obviously my HIDPI is messed up. Menus scale correctly but application titlebar and icons run at native 4k resolution.

Here is the screenshot of an "wrong" icon when scaling enabled (see wifi icon)

Any idea how to make polybar use correct icon with scaling set via profile?