perhaps centralised exchanges are aware that their days are numbered & ripping off as much as they can while its possible. i also believe that this altcoin boom might not last much longer as BTC is getting rapidly undervalued. will see..
The high transaction charges are not new,had to stop trading alt coins in some exchanges simply because of their high transaction charges one year back and they are still continuing as no one is objecting to it and they are still having plenty of customers ,either everyone has to object and stop trading altogether until they change those tactics by ripping off in the name of transaction charges when the real transaction charges are small .