If these words be the words of Christ, delivered by David in the spirit of prophecy (and as they are spoken of one person, they should seem to be so) perhaps the sense is, "when the great ones of the earth are brought down by affliction; the words of Jesus and his salvation shall then be considered dear, though now despised.
Related Commentaries of Psalms 141:6
Psalms 141:6
6 When their judges are overthrown in stony places, they shall hear my words; for they are sweet.