I am interested in further understanding the processes of valuation
and acquisition of a patent application, specifically I want to use
this information (in addition to the information that I have available
about the invention, its value, etc.) to estimate the value of a
particular patent application.  For obvious reasons, I cannot disclose
specifics of the patent application or the invention.

This is a multipart question and I would appreciate a fully formed
response (with the appropriate citations and references/resources for
further research).  I would be happy to provide clarification or split
the question if potential answerers can only address parts of this big
question.

1. How would a patent application be valued in an "appraisal"?  What
are the factors that affect the valuation of a patent application and
the relative weightings of the importance of those factors?  In the
case of a real estate property, an appraisal typically uses several
approaches such as income capitalization approach (a Discounted Cash
Flow model), a replacement cost approach, and a sales comparison
approach (sales comparables), then comes up with some form of informed
average or conclusion based on those results.

For a patent application, I could see the income capitalization
approach where the DCF analysis would be a measure of the incremental
profits enabled by the invention based on the addressable market size,
etc.  I could see a replacement cost approach that considers the time
and resources that were required to come up with the invention,
document it and reduce it to practice.  What I can’t get a good handle
on is the sales comparison approach for patent applications- I just
don’t know where to turn for sales comparables or even licensing
comparables (note: is it even possible to license rights to a patent
application, even though the USPTO has not yet allowed any claims). 
The ideal answer would contain an explanation of the valuation process
and some references to sales and/or licensing comparables for patent
applications, including some data points for completed transactions.

2. What impact would USPTO office action communications have on the
valuation of a patent application?  Prior to notice of allowance of
claims, there is substantial uncertainty about whether any or all of
the claims will be allowed.  Is there any way to estimate the
probability of allowance of claims?  This obviously has a huge impact
on the valuation of the patent application.  Is it possible to
generalize the most typical forms of Office Actions and estimate the
corresponding probability of any or all claims being allowed?  I
understand that more than 60% of applications to the USPTO result in
issuance of patents.  Are there any similar statistics available for
issuance of patents based on the typical forms of Office Actions?

3. How does an assignee of a patent application (“Original Assignee”)
transfer title to rights to a patent application, both mechanically &
legally?  Does an inventor need to approve of the assignment of rights
from an Original Assignee to another assignee of the Original
Assignee’s choosing?  I would assume that some kind of assignment
documents would be required to be filed with the USPTO to effect the
assignment of a patent application. Is this a cumbersome or expensive
process?

For the purposes of answering this question, please assume that the
invention in question (for which the patent application has been
filed) has far reaching applications and has the potential to
substantially increase the value of a market segment that today
generates annual revenues in the USA of $20 billion plus.