That is if you consider a market average 10% return. Difference between that market return and my interest rate is 7.375%, and my mortgage balance is +/- 360k. So the opportunity cost if +/- $26,550 per year.

And before anyone tries to claim 10% market return is too much I've had index funds that provided an average 10% return over a 20 year period, so I think that is a fine assumption.

And this doesn't even take into consideration that I get to deduct my mortgage interest when itemizing deductions on my taxes. So it is really closer to $30k per year that I would be missing out on.