Interesting, so instead of a down payment, you give that money to the bank as points to buy down the rate. On a $400,000 0.5% loan (bought down from 4%), that's a $2300 monthly payment with the interest portion starting at $166/month! At the end of 180 months total interest is around $15,000 plus the $16,000 (4%) paid as points = $31,000.
A traditional 30 year 20% down on $400,000 loan with a rate of 3.5% = $1437 monthly payment. But you would've paid $31,000 in interest at month 34. If you do get to 30 years, the interest is close to $200,000.