obniżyć wartość Englisch:

The pound has been devalued, so we’ll get more euros.

devalue /ˌdi:ˈvælju:; US / verb [transitive] 1 to reduce the value of the money of one country in relation to the value of the money of other countries The pound has been devalued against the dollar. ▶ dewaluować

You depreciate them by this comment.

New computers depreciate in value very quickly.