The market is low due to many of them being scholarly books not intended for general public consumption. But when they do sell, they sell for a high price some of them and some of them are rare or hard to find/get. I have 25 volumes from a series which cost about $2,500 for all the volumes I have. This link from amazon gives an idea the price individual volumes of the set sell for:
https://www.amazon.com/s?k=septuaginta+band&ref=nb_sb_noss
I have another series of 7 books, which I paid about $1,500 for. It doesn't show all the volumes on this search results page, but again here is an idea of the individual price of some of the 7 volumes:
https://www.amazon.com/s?k=dead+sea+scrolls+charlesworth&ref=nb_sb_noss_2
So all that considered then, I'd say my net worth is probably around $10,000 and all that from my books. I rounded to $10,000 because I remember calculating the value of the books in the past, but there are so many books I have its hard to have an active price valuation of it. The rest of my assets cancel each other out.