Edited to clarify last Q&A...
Great questions!
Q: Can you do the Pro Express for OEP then go per app?
A: YUP!
Q: How long does the $12.50 price go? (Does it go back to $20 on 11/1?)
A: The $12.50 is the 'regular' non discounted pricing so no worries that it is time limited. This is for the Standard implementation of course, Pro Express is lower cost before and after the free included apps have been used.
Not asked but worth pointing out; can also submit as part of user profile "Google Analytic s Key" so can gauge which marketing (SE), ads, email marketing, etc.) is getting you the most results.
Thank you...one more question...will you have access to off exchange plans?