Value? 1905 Carl Gustaf K96

You obviously mean the rifle (Gevär) with the designation m/96 (Modell 1896). Sorry to be picky, but there is no such rifle as a Carl Gustav K96, because it is not a German Karabiner. And the Swedish carbine (Karbin) was also designated m/94. Nothing with K, which was German usage, as in German the word Karabiner was often used for military rifles shorter than the "classic" long rifle, such as the Gew.98. Hence the shorter version of the same, as K98a, K98b, and finally K98k.

Anyway, getting to the price question - it all depends. There are plenty of as-new, extremely "low-mileage" m/96s around, and "in Cosmoline" does not mean that it was never fired - it could have been overhauled and put into storage, for instance. Since the m/96s in general have a very high standard of maintenance and condition, there is not going to be such a high premium for mint condition (which is often a subjective evaluation) as there would be for, say a rifle from one of the WW participants, where most examples had an active service life and an as-new item is correspondingly rarer.

Conclusion: my guess is that the market value is maybe +50% to no more than twice what a typical well-cared-for example would have in your local market.