2) When apple was trading at 8 dollars it was around 14 times forward earnings. Point being you can't just judge a company on what it's doing, but also what it's potential is. IRM is a leader in a rapidly growing and niched industry/environment.
I think it's also important to remind everyone that Buffett is in this stock. No one in the world does more due diligence than him and he's more obssessed with valuation and preservation of capital than perhaps any investor alive. It's rare that he even dabbles in midcaps, and of all of them I doubt he chose "the most overvalued" one.