I never really did the math before but I whacked something together real quick in Excel. At $0.30/THash BTC we can come up with some cost expectations for password lengths. Here I will use a 74 possible character password using 26 upper and lower case letters, 10 numbers and 12 symbols. Totally random of course. Using (Possible Chars ^ Password Length) as the number of combinations and guessing we will find our answer at about %50 of our guesses. (See! Super rough)
With SHA-256 it takes about $21 to crack a 6 character password.
$1500 to crack 7 characters.
$108,330 to crack 8 characters.
$7.8 million to crack 9 characters.
$561 million to crack 10 characters.
$40 billion to crack 11 characters.
$3 trillion to crack 12 characters.
$200 trillion to crack 13 characters.
Edit Note: BTC is kinda expensive per hash right now. Usually this would all be cheaper. Past 14 characters it could be 1 cent and still outrun the usual US budget for a couple years.