Mark-
You could -almost- accomplish what you want with the XMOD module ($90) except for #3.  I use XMOD a lot and I like it for its reliability and ability to create forms without creating new DB tables.  Unfortunately XMOD has no inherent payment gateway handoff / handshaking features so it cannot handle #3.
 
Instead, you may consider Dynamic forms ($120) which can easily do #1 and #2 and supports PayPal IPN (Instant Payment Notifications) so you can automatically allow customers to gain access to new content after a payment is verified by PayPal.  Dynamic forms has a nice drag-and-drop form builder which makes it extremely easy to create forms (much, much better than the "form Builder" option in XMOD).  Dynamic forms also allows direct DB manipulation (execute any query or stored procedure you like).  XMOD does not allow this (but the forthcoming "XMOD Pro" module will).
 
 
And a final note...
I don't know for certain which "$10,000 module" you were referring to (but I'm quite sure I can guess).  If you do consider a "professional" package for online coursework make sure it is a true LMS (Learning Management System) or LCMS (Learning Content Management System) with full support for SCORM (Shareable Content Object Reference Model).  Such a system complies with established LMS standards and allow you to import/export courses and course-related content between different LMS systems.  In other words, you won't be tied to a single solution as your LMS plus you can purchase ready-made courses to import into your system.
 
You'll want to keep an eye on the DotNetSCORM project which promises a DNN-based SCORM solution in addition to a standalone .Net-based solution.  If it gets released I'm sure it will put a big dent in the business model of that $10,000 module maker...


Hope that helps-
-mamlin

I think the "$10,000 module" should be considered more of a "system price" rather than a "module price".  I'm sure it is probably a suite of interrelated modules. I also consider DNN modules to generally be a "steal" in terms of software prices.  Most of the really good modules should easily sell for double their asking prices but developers are forced to lower prices to match the general DNN market.  Even so, $10K is extremely steep unless it also invloves complete handholding on getting DNN installed, configured and some training on how to manage DNN as well as the LMS itself.
 
If you need a true LMS with SCORM there are a number of freebie platforms under Linux/JAVA that have been developed by, used by and improved upon by a number of universities for many years so I'm not sure that it is worth $10K to most folks just to have a solution run under DNN instead of some other platform.
  
 
Content Security
XMOD certainly allows form entries (submitted content) to be secured to an individual user to one or more user groups.  I *think* Dynamic forms can do this as well (here's a link to the documentation).  
 
Overall from what you've stated I think you'd probably be happier with Dynamic forms.  Flip through the documentation and then test things out with a trial version.
 
-mamlin