I was replying to your pedantic remark 'As always: Sorry for introducing real numbers into a discussion. '. Those are not real numbers and certainly can not be checked. We have to believe you. In that case we can also believe Tom saying that thy dyno slowed him down considerably. BTW I think going from 20 to 19 mph is quite a bit for some. Bottom line is a dyno(hub) cost you 5-10 W, a battery powered light not.


Putting some numbers into bikecalculator.com suggests that the difference
between 20 and 19 mph is about 26 watts (207 vs. 181), which is a lot.