There is another thread proposing for another type of game jam, possibly it might be worth contacting this person and coordinating with him/her : Group up jam.
It could be another good idea to also contact the persons from the previous C2 game jam you mentioned to see if they are still around and would be interested in taking part/organising this one.
As for your original assessment, there are jams every week end !
You can check out this jam thread about jams that are regular. For example, this very week end is the Global Game Jam.
There is also the CandyJam that was launched a few days ago and that run up to the start of February and is kind of "a good cause".
If you're looking for a jam every week/week-end, you'll find one.
Now if you're really motivated in organising one, by all means, go ahead.
Prices are not required. Look at the Ludum Dare, the biggest game jam of them all, there is no price except a bit of promotion.
I wouldn't talk in the name of Scirra, but I'm pretty sure something could be worked out in that sense (like on twitter/featuring on their blog or whatever).
At worst, just the fact of having done a complete game in the given time is rewarding in itself you know, along the personal experience you get from making it.