what are so great about ceramic bearings to sell them at $30
They’re smoother than steel ones and spin longer.
That’s it.
Those are Ceramic KonKave bearings. They are known to center your string so it won’t go to the sides.
There are steel, and ceramic.
Ceramic is known to last longer and spin longer than the steel KonKave.
The steel KonKave is a regular KonKave bearing, but can rust like any other bearing.
The main two things Ceramic bearings do are…
Spin longer
and Last longer.
If you want to learn more, there is a page about the Ceramic KonKave bearing on dif-e-yo.com 