The theme of Job 28 seems to focus on the questions asked in verse 12 - "Where can wisdom be found? And where is the place of understanding?" These questions are asked again in verse 20. Job speaks about all sorts of secret things which are hidden beyond mankind's sight (like precious jewels, gold, and iron in the ground). One can find these precious things by mining, but where can man find wisdom? Humans walk on top of many treasures and do not know they are there. So close, yet so far away! Not even the birds, beasts, or lions have any knowledge of what valuable items are buried under their feet. Clearly, wisdom and perception in this realm are lacking.
Human wealth cannot purchase wisdom, so where can it be acquired (cf. James 1:3-5)? Consider the last section of this chapter:
"From where then does wisdom come? And where is the place of understanding? It is hidden from the eyes of all living, and concealed from the birds of the air. Destruction and Death say, 'We have heard a report about it with our ears.' God understands its way, and He knows its place. For He looks to the ends of the earth, and sees under the whole heavens, to establish a weight for the wind, and apportion the waters by measure. When He made a law for the rain, and a path for the thunderbolt, then He saw wisdom and declared it; He prepared it, indeed, He searched it out. And to man He said, 'Behold, the fear of the Lord, that is wisdom, and to depart from evil is understanding'" (Job 28:20-28).
I find it interesting that Job notes that "Death", even with its large company of men, really doesn't know much about wisdom (other than hearsay). God knows where wisdom and understanding are found. They are found in fearing the Lord and departing from the way of evil (cf. Prov. 1:7). Those who do these two things are well on their way to priceless spiritual wisdom.
God is full of wisdom and understanding. His judgment, as well as the things He allows to happen in our world to both the good and wicked, is not to be questioned.