How much time and effort may have been put in?

[Jorge_Stolfi]

How much effort do you think could have been put into the VMS text, illustrations and/or ciphers?

There are two separate questions here: (1) how long did it take the Author to create the contents -- that is, to compose the text and conceive the drawings, and (2) how long did it take to write that contents down onto the vellum sheets that are now at Beinecke.

As for (2), I am convinced that the text and the outlines of the drawings on each page were done at the same time by a Scribe distinct from the Author, who merely copied the text from a draft provided by the Author, and drew the figures according to his instructions (which may have been just "draw a different random plant on each page"), filling in the details with "inspiration" from other books.

Thus I estimate that the Scribe would take about one hour -- maybe half of that, maybe twice as much -- to do each page.

As for (1), if the contents was original research or elucubrations (which I don't think was the case), it could have taken decades.  Whereas, if the Author was merely translating or transcribing a bunch of lost texts, it would have taken less than one hour per page, too.

How much effort from the author does a theory require before you dismiss it as unlikely, and why?

The question should be whether the proposed "solution" requires substantially more effort than other methods that the Author could have used to achieve the intended result.   

Thus, in, particular, I don't care about any of the "gibberish generation methods" that have been proposed -- because they would all require a lot more more effort than, say, copying every third word of the Summa Theologica, kcab ot tnorf htiw a elpmis noitutitsbus rehpic -- and yet they would generate a gibberish text that would be much less suitable for the alleged purposes of that exercise.

And likewise I never cared about research that assumes a complicated cipher that not even the NSA and Bletchley spooks could crack.  What would be the point?  If the Author was terrified by the possibility of certain parties reading the contents, he should not have filled the book with puzzling diagrams and exotic scenery. In fact, he should not have written the book at all...

How much effort would a potential decoding require before you dismiss the cipher as unlikely, and why?

Anything above zero.  That is, I don't believe that the contents is encrypted.

All the best, --stolfi