Your spreadsheet is very depressing. It's so easy to forget how fast an exponential growth moves, I guess that's how we got a debt based currency. In 6 months my 6 Giga hashes will get me 0.08 bitcoins per day!?
What makes no sense is bitcoins need to be $1000 in 6 months for me to continue mining.
Sorry to be the bearer of bad news...

I would advise people against investing in new mining hardware at this point. It is still very profitable TODAY, but with the exponential growth not expected to decline any time soon, mining is going to have slim margins, at best, in the not-so-distant future.