While in college I worked as a bookkeeper for a magazine publisher who also dealt in rare books. I remember one day he came in and asked for a check for $75,000 to buy a copy of the Book of Mormon. He came back that afternoon with the book (he said it was 1 of 3 of that edition or something like that) and let me thumb through it. A couple of days later he sold it and I deposited $200,000 from the sale into his account. Not bad for a couple days of work.
If you ever watch any Antiques Roadshow episodes from Salt Lake City, those old and rare Mormon related books (bibles, hymnals, etc) always fetch the big bucks. Same with American Indian stuff.