Offcourse the exchange point is to generate revenue. And these fluctuations i have noted are reffering to a long range model. Not seomething that would happen many times.
To answer you unanswered question. What do you mean by conventional exchange?
So, setting the fee at the highest rationally possible is not necessary as you will not be affected too much by fluctuation, will you?
Conventional exchanges that "didn't have" your feature of automated trading, like... maybe binance, or Hitbtc.