It's a bit difficult to put a price/time on it as people still work on other things at the same time.
For example, I wrote the dialogues and set up the quest logic, one of the GPDs did all of the gameplay logic, set up the instance, cutscenes, scripting e.t.c, there was a systems guy doing loot and a couple of artists helping out with rewards. A concept artist made the loading screen, our audio guy threw in some small audio cues, and an animator ported over a monster from TSW to make a special appearance (note that this was a test to see how well it works to pull in animation rigs.)
But at the same time, I was also writing text for the TSW event, doing my normal Game Director meetings and duties. The others all had similar things going on.
Putting our focus on something that is clearly defined and is stuff that we know we can do, is fairly straightforward. And when we have cleared some of the larger features from our plate, we will be able to provide more focused experiences relatively quickly.