it has been like this for a while now. and what did you expect when bitcoin is being advertised on the media and every big and small players are talking about it, that attracts a lot of money towards bitcoin. despite the current fall the buy support is strong and huge because of all that.
and by the way it is $5.5 billion dollar in past 24 hours according to coinmarketcap.com which adds the volume of all the exchanges. about $900 million of it belongs to bitfinex
At such volume of $900 million per day, the profit of these exchanges are fabulous. There is arbitrage profit as it should be written into their trading platform - sure win;then the transaction fees. Platform market making is again a no risk profit.
I know how to write the software for a trading engine. But how to get the license to run one? What initial capital needed?