Banks by definition have 10-15 leverage ratio, called gearing. It is mesured as RWA (RiskWeightedAssets) ratio to Equity(BookValue);
If a 10 times leveraged bank lost just 10% of RWA by way of recession, crash, etc.(which is a lot), they lose all their Equity. And by law they must bankrupt.
The bank is risky business; and their pricing reflects this fact, particularly when investor's sentiment becomes extremly risk-averse, just like now.
To demonstrate how extrem risk-aversion Is:
1)Currently the bank's pricing equation is (using multiple linear regression) cca. Price=0.9*Bookvalue+5*Dividend% And othertimes important factors like Earnings, Growth, etc. are absolutely insignificant.
2)Longterm, the pricing equation is cca. Price=2*Bookvalue+6*Earnings+1.5*Div%