Comment by polymathemagics

Yeah, and for a lot of earners in high tax states, the effective interest rate you pay is essentially almost half off thanks to the mortgage interest tax deduction. If your marginal tax rate across federal / state / local is high (mine's 46%), then you can get back almost half the interest. Which shortens the gap between a 3% vs 6% mortgage, the effective difference being more like 1.5% than 3%.