When is the top of a mountain like a bank account?

“When you have a lot of money”

This guess focuses solely on the financial aspect of a bank account, missing the play on words involving 'peaks' and 'interest'.

“When you climb it”

While climbing a mountain may seem relevant, it does not connect to the idea of 'interest' or 'peaking' in the context of the riddle.

“When it's windy at the summit”

This answer is based on a physical characteristic of mountains rather than the clever wordplay about 'peaks' and 'interest' that the riddle emphasizes.