If we start with a $250K house and a $200K mortgage at 5.5% over 30 years, assuming a 25% tax bracket, the present value of the mortgage interest tax deduction is about $35K (discounting at 5.5%) over the life of the loan. (I made some crude assumptions to simplify the calculation that could swing the numbers by a couple thousand dollars in either direction.) That amounts to about 14% of the value of the house. That’s a meaningful number, but I agree the whole concept/rationale is over-marketed.