There are Originals, there are Reprints, there are CDs and there are Photocopies.
CDs and Photocopies I wouldn't pay more for them than they cost to produce.
Reprints are nice as they do replicate the look and feel of the original. Someone thought that a "Surplus City" reprinted Jeep parts book must have been the real thing at the Dubbo auction because they paid something like $150 for it. You could get a fresh unread one from Surplus City for US$30!
Originals are nice because you know they are the real thing (Reprinters sometimes change some small detail to distinguish it from the real thing eg manual for the "Boyes" rifle). Not only that, they have a rarity and collectibility in themselves as there were only a certain number printed and that number will always diminish, a bit like rare stamps. Some recent examples like
this LP2A parts book are available elsewhere as photocopies, but how many of the originals would be still be in existance? 1 or 2 hundred copies? Large run manuals such as MB-F1 or MB-C1 can still be found at swap meets for $20 to $30 in good condition.