Worth

In 1 Nephi 5:21, Nephi says

And we had obtained the records which the Lord had commanded us, and searched them and found that they were desirable; yea, even of great worth unto us, insomuch that we could preserve the commandments of the Lord unto our children.

It seems that this realization is what inspires Nephi to write about his own record just a few verses later

Wherefore, I shall give commandment unto my seed, that they shall not occupy these plates with things which are not of worth unto the children of men.(1 Nephi 6:6)

These are the first two uses of the word, "worth" in the Book of Mormon. The next is in 1 Nephi 13:23, where Nephi in vision sees the coming forth of the Bible and says it will be of "great worth unto the Gentiles". Interestingly, the first three uses of that word in the Book of Mormon refer to the worth of the brass plates, the plates of Nephi and the Bible, respectively.

In fact, most of the 17 uses of that word in the Book of Mormon are related to the scriptures and especially the coming forth of the Book of Mormon as part of the marvelous work in the latter days. Some examples:

And after our seed is scattered the Lord God will proceed to do a marvelous work among the Gentiles, which shall be of great worth unto our seed (1 Nephi 22:8)

confine the words unto mine own people; for I know that they shall be of great worth unto them in the last days (2 Nephi 25:8)

And the things which shall be written out of the book [of Mormon] shall be of great worth unto the children of men (2 Nephi 28:2)

When Moroni decides to write more, contrary to his initial plan, it is only because he thinks his words might be of worth

I had supposed not to have written any more; but I write a few more things, that perhaps they may be of worth unto my brethren (Moroni 1:4)

The Book of Mormon authors are very clear: The scriptures, including their own engravings are of great worth. Nephi acknowledges, however, that the definition of "great worth" is highly subjective

But behold, there are many that harden their hearts against the Holy Spirit, that it hath no place in them; wherefore, they cast many things away which are written and esteem them as things of naught. But I, Nephi, have written what I have written, and I esteem it as of great worth (2 Nephi 33:2-3)

For the things which some men esteem to be of great worth, both to the body and soul, others set at naught and trample under their feet. (1 Nephi 19:7)

Zeezrom, for instance, initially was one of those setting "at naught" the word of God as Nephi described, and claimed that his silver was of "great worth" (Alma 11:25). Contrast that with Moroni's message:

And I am the same who hideth up this record unto the Lord; the plates thereof are of no worth, because of the commandment of the Lord. For he truly saith that no one shall have them to get gain; but the record thereof is of great worth (Mormon 8:14)