When I crunched the numbers for the mortgage interest deduction it really didn't seem that compelling. It replaces the standard deduction so the first 12,500$ in mortgage interest does nothing for you. After that it's just a minor reduction in taxable income and your tax burden is only reduced by a fraction of your mortgage interest. Not enough to cover the costs of maintaining a home and the tendency to consume more…
With that said, as a lot of people said, in high cost areas, it goes really quick, especially if you add municipal taxes which can also be deducted. So if you have 500 bucks a month in municipal taxes (which is kind of low in high cost areas), you're already halfway there. Add the interests (often half of your mortgage payments), and you're well beyond.
If you're in an area with million dollar houses being quite common (we are talking about the rich poor gap after all), you're talking about a 30-40k deduction easy, and even more for super rich.
One thing beyond that (any accountant in the crowd correct me if I'm wrong), the mortgage interest deduction for your primary residence is special in that it is one of the deductions that can be applied to AMT. So again, it helps the ultra rich.
I'm no 1%, but I am affected by AMT, and my place is in a high cost area, and this tax deduction is the only thing saving me from crapping my pants every year when I file my taxes.