If you expect rates to come down soon, you can plan to refinance in the future, but that’s a gamble. Rates may not go down, or the value of the house could go down before you refinance, which may make refinancing more expensive depending on how much you owe.
Paying down a high interest mortgage will always have bigger impact on the dollar than paying down a low interest mortgage.
I’m comparing a mortgage with a high rate and lower principal to one with a lower rate and high principal, where the minimum monthly payments are the same and the owner pays the minimum.
A high interest mortgage just means that you pay more total interest over the life of the mortgage. In any case traditional mortgages are front-loaded, so you pay more towards interest up front than you do principal.
An optional extra payment is worth more when interest rates are higher.
Ie. An optional extra payment of 1000$ will pay your 150$ a year in saved interest when the rate is 15% and only 15$ when the rate is 1.5%.
Everything else being equal, optional payments has a higher value, which represent value to the buyer.