Just went down a rabbit hole looking at mortgage interest rates from september 2024 and honestly the numbers are pretty wild when you actually do the math. Back then the average 30-year fixed was sitting at 6.69% - doesn't sound crazy now but that's a solid chunk of change over 30 years. I ran the numbers and on a 100k loan you're looking at like 644 a month just for principal and interest. Over the life of the loan that's roughly 132k in interest alone.

What caught my attention was how the 15-year fixed was only 5.74% at that same time. Shorter term, lower rate - makes sense but the monthly payment jumps to 830. So you're paying almost 200 more per month to cut 15 years off the loan. The trade-off is you only pay about 49k in interest instead of 132k. Kind of puts things in perspective when you're thinking about refinancing.

The mortgage interest rates september 2024 data also showed jumbo mortgages were at 6.75% which is basically just slightly higher than regular 30-year rates. On a 750k loan that's like 4,864 a month before taxes and insurance. That's a whole mortgage payment by itself for most people lol.

What's interesting is understanding how these rates actually get set. The Fed obviously plays a huge role - when they move rates up or down, mortgage rates tend to follow. Bond yields matter too, especially the 10-year Treasury. Plus your personal credit score and debt-to-income ratio can swing your rate by a full percentage point or more. If you're sitting at like 620 credit score versus 750, the difference adds up fast.