Bitcoin's BTC$62,341.57 volatility is cheap, particularly on the bullish side, heading into Friday's $10.5 billion quarterly options expiry, according to dominant derivatives exchange Deribit. The exchange's bitcoin volatility index, DVOL, which measures the annualized 30-day expected, or implied, volatility, is trading at 41.5%. That's well below February's peak of 90%, though not quite as cheap as May's lows.