My thoughts are not your thoughts... — The assertion refers to both the promise and the warning. Men think that the gifts of God can be purchased with money (Acts 8:20). They think that the market in which they are sold is always open, and that they can have them when and how they please (Matthew 25:9-13).
Related Commentaries of Isaiah 55:8
Isaiah 55:8
8 For my thoughts are not your thoughts, neither are your ways my ways, saith the LORD.