What does the phrase 'infinite good is being bought' mean?

Directions: Answer the question based on the following passage.

The treasure of wisdom and science, which all men desire by an instinct of nature, infinitely surpasses all the riches of the world; in respect of which precious stones are worthless; in comparison with which silver is clay and pure gold is just a little sand; at whose splendor the sun and the moon are dark; compared with whose marvelous sweetness honey is bitter to the taste. In books I find the dead as if they were alive; in books I foresee things to come; in books warlike affairs are set forth; from books come forth the laws of peace. We must consider what pleasantness of teaching there is in books, how easy, how secret! How safely we lay bare the poverty of human ignorance to books without feeling any shame! They are masters who instruct us without rod or ferule, without angry words, without money. The value of books is unspeakable; no dearness of price ought to hinder a man from the buying of books, if he has the money that is demanded for them, unless it be to withstand the malice of the seller or to await a more favorable opportunity of buying. For if it is wisdom only that makes the price of books, which is an infinite treasure to mankind, and if the value of books is immeasurable, how shall the bargain be shown to be dear where an infinite good is being bought?