I generally have to agree with Martin here, although I think he meant "refined" instead of "refinanced"
Confluence and JIRA are priced low, IMHO, compared to the value they bring (look at the price of Confluence vs. Lotus Connections for instance). This helps growth and adoption, and it's a valid market strategy. Extra plugins on top are priced both to fund their development and because this helps offset the low price of the original software.
The Calendar plugin was nice when it was free, but to be honest, I discouraged users from relying on it specifically because it was a freebie and not open source. I knew that Atlassian could stop development on it at any time (not that many didn't use it anyways, which means I have an unfun manual upgrade coming up, unless an automatically-upgrading version is released soon), and I wouldn't really have any right to be angry with them for this, nor would I have recourse or an upgrade path without the source code.
To me, the new product looks like it brings a lot of extra, useful features. Yes, it's costly compared to Confluence, but that's comparing apples with oranges; it's not costly compared to many other group calendaring solutions (Oracle calendar, Exchange).
Did I mention I need it to support CalDAV?