This verse clearly teaches that all believers must go to college. Just kidding. I’m not sure paying for a formal and institutional education was the norm at this time. Besides that, one would be assuming that such an education would offer truth and wisdom!
So how does one buy truth? He does not literally buy truth. This is figurative language for counting the cost. Truth and wisdom must be diligently sought. We are not born with it uploaded into our brains. It requires time, energy, concentration, work, and diligence. It is not always easy. But it is worth the price. Truth and wisdom are worth any earthly resource one possesses. Thus, one also is not to sell it. It is possible for one to choose to keep such earthy resources instead of gaining wisdom. Or one may even forsake the truth and wisdom one has obtained to chase after such temporal goods.
I am finally done with my formal education. But I am committed to being a life-long learner. I will read, study, discuss, experiment, practice, listen, write, and observe till I die. I am on a mission to discern truth and gain wisdom at every turn.