Ok, I'm going to bump this, because I wanted people to know:
One of my clients and I were chatting about CCCs, and they mentioned that they'd just applied for a Cap 1 card about a month ago via a pre-approved mailing. They were shocked when they got a $30k credit line! That's only the second I've heard of, along with this thread's OP. I'm embarrassed to admit I didn't even believe the original poster of this thread. My bad...sorry.
What surprised my client was that Cap 1 asked for household income; rather than just their salary alone. Their HHI is over $150k. Sooooo....I guess Cap 1 DOES give out $30k credit limits. Just on one card, though, it seems, from their website.