I have been developing for Drupal for 5 years, with a portfolio of many large scale projects. I am also the author of some popular Drupal modules.
With all that said, in my experience, Drupal offers zero TCO or ETA advantage over Django or Symfony on any medium to large project. A lot of the great things you may hear about Drupal are coming from either (a) Non-developers or (b) People who have staked their careers on Drupal.
A few reasons why Drupal cannot be taken seriously include...
1) Lack of unified model layer and no ORM. The recent efforts to implement schema definitions are still, unfortunately terrible. All content types should be able to be defined as a model, including CCK fields.
2) Over-reliance on Views and CCK modules. These are just fancy interfaces for a model layer. They are great for non-developers, but in no way compare to a proper model implementation. At the end of the day, you will save zero time by implementing a Drupal View over implementing a simple ORM call. Views and CCK slows down development.
3) Lack of any solid deployment procedures. Ever tried merging changes between different Drupal configurations?
4) Using native PHP as the templating language. This causes more headaches than one you can possibly believe. A proper templating language should be used instead which will prevent lazy or incompetant developers from adding business logic into templates.
5) An army of incompetant, unexperienced developers contributing sub-par modules.
6) Lack of any kind of namespacing whatsoever. "De-Facto Namespacing" is a pile of shit.