This looks like a nice set complete with errata sheets! It is hard to gauge the condition of the box and books strictly from the one photo, but it appears solid. The obvious defects impacting condition are the browning of the top box label (outlined by a book or box on top) and what appears to be staple rust on all three books.It is hard to tell from the photo, but I would open the books and check for writing, smells, defects, smudges and the condition of the staples and if the rust stained the paper.

Even with these issues, I would expect $5k to $7k for a set in this condition. In order to tighten the valuation, please post some more photos of the box (top, bottom, sides, corners, and interior) as well as more detailed photos of the books showing front, back, the staples inside and out, the copyright pages, and any other defects.

The Chainmail is a second print of the third edition, and in that condition, I would guess $75 to $150 assuming no major interior defects.

Let us know if you have further questions.