Is my return on discount points calculation correct?

[Konstantin Klitenik]

I'm taking out a $740k mortgage at the end of Feb.  I have the option of 4.25% with no points or 4.125% with 0.5 points ($3700).

Using bank-rate mortgage calculator, I looked at principal and interest about 5 years out (end of 2024).

With 4.25 and no points:    Principal $80,802  Interest $173,997

With 4.125 and 0.5 points: Principal $82,324  Interest $168,695

So putting $3700 towards 0.5 points now, will save me $5,302 in interest and add additional $1522 in equity.

This nets $5,302 + $1,522 - $3,700 = $3,124 (84%) return on $3,700 in 5 years.  

That seems like a very good deal.  Am I missing anything?

Thanks.