Complete years ought to be $20-$25 (except 1943 & 1944 at $30+) in very good or lower condition. Add approximately $1 per issue for each grade better than vg, and probably deduct $1.50-$2.00 per issue for any grade lower than good minus. Lots of dealers will ask $10+ per issue, but that is basically ridiculous in my humble opinion. It is a very subjective question, but if I had the time to pull them, I'd offer the decade all in good to very good condition (the fraying and cracking of spines you describe, possible some dog ears or slight fading) for $125-$150 plus shipping. I am not offering it, because I don't have time to assemble such a set from my duplicates. While signicantly scarcer than later issues, the war years are not that hard to obtain, though all really nice issues for the decade with supplements all well preserved can command a premium
Note: Any sales or trade arrangements are solely between users of this site; The National Geographic Society is not a party to and does not endorse or promote any particular sales or trade arrangements between collectors, dealers, or others. Due to the immediate nature of this medium, National Geographic Online also does not review, censor, approve, edit or endorse information placed on this forum. Discussion boards on National Geographic Online are intended to be appropriate for family members of all ages. Posting of indecent material is strictly prohibited. The placement of advertisements or solicitations unrelated to National Geographic also is prohibited. National Geographic Online shall review information placed on this forum from time to time and delete inappropriate material that comes to its attention as soon as it is practicable, but cannot guarantee that such material will not be found on the forum. By posting material on this discussion board you agree to adhere to this policy prohibiting indecent, offensive or extraneous advertising material, and to legally assume full and sole responsibility for your posting.