I think all of these mining stocks are undervalued. There just isn't enough money in the system to support the 'proper' prices. So, for now they remain immensely profitable. Not enough people know about these stocks, or perhaps are concerned about putting their money in 'virtual' exchanges that theoretically give you no legal rights (according to the TOS)
I disagree. bitcoin as proper "money" has a price. Thus investment opportunities have to compete with the price of money.
Your perception has been altered by the fact that we live in an era of "cheap" credit, where banks and people "throw" money at any investment opportunity they can. The fiat money we have today doesn't have a price anymore. In fact, the price of fiat money is negative. In a commodity money system like bitcoin, the price of money is positive.
addendum: Actually there are strong indications that we live in a money price apartheid, where a selected group of individuals has access to money without a price (big inflation), while all others pay an ever increasing price for money (deflation).