As per the post above - they generally have lighter non-contact seals. They also tend to have lighter grease / oils.

I guess you could go steal ceramic bearing seals and put them on steel bearings. You could clean steel bearings and replace the lube. Or just cut the seals off the steal bearings and clean and use light oil - you'd likely be worse off than just buying ceramic.
Full ceramic un-lubed un-sealed can be had for ~$20 these days. You are paying for the other stuff.

I do take the seals off my steel bearing on the inside where there in no opportunity for dirt.

But under force and speed that 10% friction number changes. At near static (stopped) the seals and grease are most of it. With 90RPM and 400W on them - or 1,000W+ in a sprint, some riders say they can feel them. Whether they can, or can't that they think they can is a good thing.