You're looking at more like 5+ billion/sec today. There was a listing of modern consumer video cards + their hashing capabilities posted on another HN story recently, but I can't find it.
"Hashes" aren't interchangeable, they're an abstract concept. In this case, the thread is talking about the SHA-1 hash algorithm. AFAIK Bitcoin uses SHA-2 w/256-bit digests.
So, actually, in this case the two happen to be related but different - SHA-1 being considered potentially flawed but not (yet) the stronger SHA-2.
Also, the Bitcoin block headers that are hashed are (I think) 80 bytes (640 bits) long, salted passwords probably a bit shorter.
Wikipedia says SHA-256 runs about 2/3 the raw throughput of SHA-1. You can the comparative rate yourself on any nix computer:
$ openssl speed sha1 sha256
-snip-
Doing sha1 for 3s on 16 size blocks: 7760096 sha1's in 2.99s
Doing sha1 for 3s on 64 size blocks: 5502820 sha1's in 3.00s
-snip=
Doing sha256 for 3s on 16 size blocks: 5460366 sha256's in 3.00
Doing sha256 for 3s on 64 size blocks: 3169031 sha256's in 3.00s
-snip-
*
So... about 2/3 faster. I don't know enough about crypto implementation, but I'd guess this ratio would scale roughly to the much faster GPU implementations as well.
Yes, I have 2 6950s, which together average to about 660MH/s on hashkill mining bitcoin, but when I tried MD5, IIRC they averaged to about 3200MH/s. I'd assume SHA1 to be slightly slower, but not much.
Not sure if this is what you were looking for or the particular hash bitcoin uses, but a $110 Radeon 5830 can get you around 250Mhash/s