They are probably both stringing each other along and playing a game to see what the other side does. This is might be not unlike the HBGary incident.
If Anon are at least mildly intelligent they'll figure out this is a sting operation. Slowly trickling in money then following it to the source is most likely an FBI setup.
Now Anon could keep playing this and accept money but provide some random bank account just to see what Symantec does.
Actually, to think about it, their best possible exit out of this is to ask this money to be sent to a charity, or a foundation. For example, "Donate $50k immediately to EFF and we'll promise we'll erase the source files".
But then going by their previous patterns they'll probably release the source anyway.
I don't know, but if this is an FBI sting they are not very ingenious. "We'll give you money in the course of 3 months as continuous payments... you'll have to provide proof you deleted files.. really?". A 10 year old can figure out what this is. Kind of disappointed at the quality of their work (and our tax money's use).