Yes, price will have a huge effect on the numbers. I recall Vitalik saying something along the lines of "the network could survive even at $30-$50 ETH a year out" at one of the recent meetings. How in the world he calculates this, I will never know.

1:16:30 talks about issuance decrease
1:20:30 talks about difficulty
1:21:30 question about extreme price decrease + Vitalik's response ($20-$50 range, wtf?)

It's just so weird to me that they talk about this stuff so lightly when the security of the network is directly tied to these numbers.