Can We Monetize MMO's Via DLC?

"The use of a free-to-play monetization model requires careful placement of your best content, what I call "carrots," on the other side of payment opportunities that I call "gates.""
 - "Game monetization expert Ramin Shokrizade", writing for Gamasutra
We've had a week to process the bombshell of SWTOR's sudden (albeit in development through November) planned change in business model.  Many of us, myself included, have thrown out roughly the same ideas about how the game's solo leveling story content was its best feature, while its endgame appears to be failing to retain players. 

For the sake of argument, I will assume Mr. Shokrizade means that Bioware should have monetized access to the story missions, which he calls the "best parts" of the game.  I was fumbling around the same suggestion a few months ago in light of rumors about a potential added fee for the game's forthcoming new planet - this seemed inconsistent with a subscription model, and I had assumed that they would not take the subscription off the table so early.  Could selling access to content throughout the game - perhaps on a planet by planet basis similar to LOTRO's model - really have doubled or tripled Bioware's revenues?

I'm not convinced for a number of reasons. 
  1. It would be hard to justify the $60 fee for the box if very little of the content were included.  While retail definitely ate a chunk of this revenue, we know that over two million copies were sold.  That's a lot of microtransactions. 
  2. Just as charging the monthly fee rewards players for finishing early, charging by the planet rewards players for skipping optional content or quitting outright if they're not loving the story.  Offering up opportunities to quit every few levels might not be in the developers' best interest, especially if you run into players like myself who struggle to find a class with both a good story and fun mechanics.  
  3. The real issue, though, is development costs.  Say that Bioware could have sold the base game with just the Act I stories but no subscription for the full $60 and charged some amount of money per planet per class thereafter.  This doesn't add up to much more than the revenue they get from their single player offerings and paid DLC, which cost much less to develop.  Further, adding more planets in the future may well be cost prohibitive (a theory that I suppose we are about to test).  
Alternately, Mr. Shokrizade may be implying that Bioware's mistake was developing this kind of game in the first place.  For SWTOR, we know that the subscription model did not pan out, and I stand by my initial reaction to the new plan - confusion about how a model which does not charge for story content fixes the problem of players beating the story content and then quitting.  (Tobold seems to agree.)

Meanwhile, for all the hype concerning the performance of Turbine's approach to free to play, which is roughly what we're discussing here, there are some signs that Turbine may be struggling with the sustainability issue.  We are seeing both point bundles and expansions bundled into larger and more expensive packages, while more and more power is added for sale in the store. That said, if the answer really is that we can't have games like SWTOR because there is no way to make them commercially viable, that's a pretty big disappointment for the future.