[Another_Act_]

> In other words, inflation means what you're paying back to the bank is worth less and less as the time goes on.

Well yes, that's exactly my point. The $1 you pay back to the bank 25 years ago is worth MORE than the 1$ you paid yesterday. But you still only need to pay back a fixed $300k.

Obviously agree that interest paid is where the bank charges you for the loan, but your original point about inflation meaning your actually paying back the inflation adjusted value of the loan makes no sense.

[Etheryte]

I think this phrasing misses the point. If you paid back anything less than the inflation adjusted cost, the bank would lose money on the loan. Hence, the minimal amount you have to actually pay back is the inflation adjusted cost at the end of your mortgage, simplified to the 600k in the above comment. In the real world both inflation and interest happen continuously, but it's easier to exemplify without that fact.