^^^
That sounds about right. There is no logical reason why it would be more than that. All you are doing is increasing the tolerance of the ball bearing a bit, and using a lighter grease. Ceramic bearings have use in applications that are either: high load, high speed, or high shaft tolerance. A bicycle BB has none of these needs.
When you spin the crank slowly on the work stand, all you are seeing is that the lubricating grease is lighter, and the seals on the bearings are looser. This loses all meaning once you are putting a lot of torque on the crank at speed. 200rpm is a pittance when talking about the world of ball bearings. These things are made to run at thousands of rpms in motor applications and the bicycle application kinda just hitches a ride on that infrastructure.
The only legitimate reason why you might get ceramic bearings is that they might last longer than steel ball bearings because the ceramic is harder than steel. In the bottom bracket application, other than the lifetime, there are no performance advantages to be gained by running ceramic ball bearings.
The effect you are feeling in sprints and stuff is, unfortunately, just a placebo effect. If someone snuck into your house tonight and switched your bearings out to be steel, you'd not even notice it.
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Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --
the tiniest sprinter