I'd ball park at least 150k for 30 seconds. Ok, it they can't pay it, let them know that that is what is is worth. Then, negotiate a cash payment of what you can afford to live on, replace your equipment, etc. (should work out to at least $50/hour-its not just food and rent, but replacment of equipment./softeare/etc.). Ok, then negotiate the difference between 150k and what you get at $50/hour, and take that as residuals (a percentage of the profits of the video). This lets them get the video done on the budget they have, while letting them know that your (and by extension, the rest of use 3D animators;-) talents are worth a good deal of money. Don't bank on the residuals paying off, they usually don't. But hey, there is always a chance that it will be the next BlairWitch (hopefully with better lighting and camera moves;-).