A business Case for Enterprise Python
There is -- almost -- no usable "Business Case" for any technology choice.
"what about a large MNC that already has a lot invested in Java"  Ask around.  See if there's a business case for Java.
I doubt you'll find anything.  Most companies drift into technology choices slowly.
There was no business case for COBOL -- it was the only game in town in the olden days.
There is rarely a business case for Java.  What usually happens is that some visionary individual started building the first web site (probably in Perl).  The "web thing" gained traction, and some vision individual started building web sites in Java.  Eventually, the success of those small teams indicated to others that Java had advantages over COBOL.
Managers say the words "make a business case", but watch what they actually do.  They listen to (1) their peers, (2) successful people.  
To make the "business case" for Python, you have to be that visionary individual.
1) Use Python.
2) Be successful.
3) Share your successes.
4) Be prepared to explain that your success is due to your tools, not your personal level of genius and charisma.
This will not be a "programming" question but more technology / platform related question. I'm trying to figure out whether Python can be a suitable Java alternative for enterprise / web applications. 
Which are the ideal cases where you would prefer to use Python instead of Java? How would a typical Python web application (databases/sessions/concurrency) perform as compared to a typical Java application? How do specific Python frameworks square up against Java based frameworks (Spring, SEAM, Grails etc.)?
For businesses, switching from the Java infrastructure to a Python infrastructure .. is it too hard/expensive/resource intensive/not viable? Also shed some light on the business case for providing a Python + Google AppEngine based solution to the end customer. Will it be cost effective in an typical scenario?
Sorry if I am asking too wide a question, I would have liked to keep it specific, but I need your help to evaluate Python as a whole from the perspectives of the programmers, service providing company and end business customer.
For an SME, a Python/GoogleAppEngine based technology stack is a clear scalable and affordable platform. But what about a large MNC that already has a lot invested in Java.
Thank you so much. I am researching this myself and will gladly share my conclusions here!
Thank you,
Srirangan