<prompt> Human: My lender has offered to decrease my interest rate on a 200 k mortgage from 4.75 to 4.625 for 1,575. Is this a good deal? She says my monthly payment would be 16 per month less , and I would break even after 8 years. It seems fishy because how much of that 16 savings would be interest paid to the bank, and how much would just be me paying myself? Im having trouble visualizing this. Also she says nothing about opportunity cost. I put extra money in index funds usually.  <response>: Im not exactly following your whole opportunity cost concern.Shes definitely correct that in year 8 you will reach your break even point. So if you take the full 30 years to payoff the mortgage, not buying the lower rate is gonna cost you a little over 4K.If you dont plan on living there for 8 years, then obviously dont buy the better rate. 