Manuals. How much is too much?

[Ryan]

G'day guys (and girls?),
As alot of us do, I been watching a lot of items on ebay lately, including original manuals for CMPs, willys jeep etc. A couple of examples recently being $255 for a willys jeep manual and $96 for a 1943 CMP manual.
Now I know it depends on rarity and demand but how much is too much to spend on an original WW2 manual? What are some of the prices you guys have paid? Or what are some of the other prices you have seen?

And finally, glad to be here.
regards
Ryan.