It boils down to risk tolerance. If Elon Musk were to say "I'm thinking of doing something new, just not sure what yet", someone will throw $7.5M at him. On the other hand, if you're not a big name with an established track record then showing up with just an idea isn't going to get you very far. The more you can demonstrate to reduce risk, the more likely you'll be in successfully raising funds.
Since you brought up Elon Musk, the "seed" funding for SpaceX was $100M of his own money. A different industry for sure, but I think it proves that "seed" funding can't really be defined by the amount but the intent.
Very true. I wasn't addressing what is defined as a seed, but his second point asking "How far do SV angels expect you to be before they'll put that kind of money on the table?"
