Cost estimate of a manual as if it was outsourced

[SB]

OK, so my boss discussed with the Marketing Director the shortage of
personel in technical writing and his comment was "a problem with time
managment". Well, the Marketing Director plays the "I have no idea how much
time it takes and what is involved". I sent him a presentation with an excel
table as to how to estimate how long it takes. According to that, the two
technical writers are doing about 100 times more than they are supposed to
do in a fraction of the time. However, since they don't know how much is
involved, you can work around the clock, which is what we do and are not
able to meet the requirements.

So, to make a case which will be more appealing to the Marketing Director,
my boss wants me now to estimate how long would each thing take if it was
outsourced. He wants to know the total cost of a manual.

For example:


   - 10 photos + photoshop editing will take 30 hours = $XYZ
   - Visio drawings ... = $XYZ
   - Document new features take ... = $XYZ
   - Time taken to update the document to reflect the new features will
   cost $XYZ
   - Edit, format the document will cost $

= Total cost

OK, so how do I go about calculating this? I am employed, not a freelancer.
I know that everybody works at a different speed but can you tell me in the
average how to estimate this?