Exactly. Even at the lowest transaction volumes MtGox charges 0.6%, so the operator can capture 15bps in each direction.

That said, customers still face risk that the operator could use the deposits for expenses, or for dividends. I'm reminded of Full Tilt Poker, where customers were told their funds were in segregated accounts, but the funds had actually been given to the directors.

The issue was undetectable until outflows outpaced inflows and the music stopped.