Official announcement about the fee...

https://twitter.com/cex_io/status/396262937922646016

"The estimated fee is 0.000000002695 BTC/share, which makes it ~4% of total mining profit."
(from https://cexio.zendesk.com/entries/28208413-Official-statement-about-the-maintenance-fee)

4% of profit...close to some pool fees, except they're actually charging in USD and then converting to BTC so it will vary based on the exchange rate.

Trading at almost 0.108 per ghash - looks like the news has not gotten out very far.