When I refi'd last year, the mortgage company's quote tool required a credit score along with the other data. I just tried at - from 770 to 730 would cost $900 extra in closing costs at the same rate/term/all other factors. That's probably the biggest hit you'd see, IME. Insurance rates, etc., probably are $20-40/yr if anything. 730 is still in the very good, though not top, tier.