IRR of paying points to buy down rate on a loan = 26%??

[Jacob Stephen]

I am debating paying points to buy down rate on a loan.  The property is a multifamily investment which I intend to hold onto for 10+ years.

I am getting quoted 1 point to buy down the loan 25 basis points.

Lets say the base rate on a $100,000 30 year amortizing loan is 4%.  I can buy down rate to 3.75% for $1000.   (100,000 x 0.25%)

In Microsoft excel, I can calculate the monthly interest payment in each scenario (4% vs 3.75%) for the 360 periods(12 months x30 years) using the IPMT function.  

I can then calculate the difference in interest payment for each period. This translates into my monthly savings. I then use the IRR formula to calculate the internal rate of return on the $1000 upfront investment. Since the savings are monthly, I annualize the savings using (1+ Monthly IRR)^12 -1.

The number comes out to 26.69%!!! 

This seems like an insane return provided i hold onto the property.  Am I doing something wrong?  Are there other factors I'm missing?

Thanks